Forces And Matter - Physics For Class IX (Science Group) - Question Answers

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Physics For Class IX (Science Group)
UNIT 5: FORCES AND MATTER
Questions Answers

Q.1: Define Force and its type? What can a force do. Give some examples?
Ans: FORCE:
Force can be defined as:

"A push or a pull that changes or tends to change the state of rest or uniform motion of an object or changes the direction or shape of an object."

OR

An object at rest needs a force to get moving; a moving object needs a force to come in rest or change its velocity or direction.
Thus force can be defines as:

"Force is the agent that changes the state of rest or uniform motion of a body."

In short,

• Forces on an object can cause tensile deformation (stretching) and compressive deformation (squashing).
• Force is required to change the position, state or shape of an object.
• Force can act as pull or push agent.
• Force produces acceleration.
• It can produce distortion.

Nature:
Force is a vector quantity. It is denoted by "F".

Formula:

F = ma

Where,

• F is force applied on a body
• m is mass of a body and
• a is acceleration of a body

Unit:
In SI system, unit of force is Newton (N) or kg-ms^-2.

TYPES OF FORCE:
There are two type of forces:

1. Force (action at distance):
   e.g. Gravitational force, Electrical force, Magnetic forces, strong nuclear force.
   
   
2. Force (contact forces)
   e.g. Frictional force; Tension force; Normal Force; Air Resistance Force, Applied Force, Spring Force.

Examples Of Force:

• Force is needed to move a car.
• Force causes the spring to stretch.
• We need force to move some luggage.
• If we bend our plastic ruler we will change its shape.
• Force applied by hands on the dough changes its shape.
• A spring can be stretched or compressed by applying force.

Q.2: What are the effects of a force on solids?
Ans: FORCES ACTING ON SOLIDS:

• Solids have definite shapes and sizes, however it is possible to change their shapes and sizes by applying external forces.
• When the external force is removed, the object tends to return to its original shape and size. This behavior is called elastic behaviour (elasticity).
• The effect of a force has, depends on the materials involved. Soft materials, such as rubber can bend and flex very easily.
• A spring comes back to its original shape when we remove the force. Materials like this are called elastic.
• Solids can be stretched, squashed, bend or twisted. A sufficiently large force will permanently deform or break an object.

Examples:

• A Force can twist an object, like twisting a wet cloth.
• A Force can bend an object, like bending a iron rod.
• A force can deform an object, like Crushing a tin can changes its shape and size.

Q.3: Define elasticity, elastic force and elastic limit? what are elastic materials. Give example also?
Ans: ELASTICITY:

"Elasticity is the property of a body to regain its original shape and size when deforming forces are removed."

In other words,
External forces are applied to change shapes and sizes of an object. When this external force is removed, the object tends to return to its original shape and size. This behavior is called elastic behaviour or elasticity.

ELASTIC FORCE:
The force applied to deform the shape of an object is called the elastic force. Or An elastic change occurs when an object returns to its original shape and size after the load is removed.
For example:
When we pull on the band, it stretches but doesn't break. The resistance we feel when we pull on it is elastic force. The farther we stretch the band, the greater the elastic force. After we stop pulling the band, it returns to its original shape.

ELASTIC LIMIT:
Hooke's law is applicable to all kinds of deformation and all types of matter i.e., solids, liquids or gases within certain limit. Such limit is called elastic limit. It can be define as:

"Elastic limit tells the maximum force or stress that can be safely applied on a body without causing permanent deformation in its length, volume or shape."

In other words,

"Elastic limit is a limit within which a body recovers its original length, volume or shape after the deforming force is removed. Beyond this limit spring deforms permanently."

ELASTIC MATERIALS:
Soft materials are flex very easily and return to its original position when we removed external force, Such materials are called elastic materials. Such as:

• Rubber can bend and return to its original shape very easily when we removed external force.
• A spring comes back to its original shape when we remove the force.

Q.4: How solids are deformed?
Ans: DEFORMING OF SOLIDS:
To explain that solids are deformed, let us perform an experiment with the spring.

• Consider a spring hung from a rigid support, so that its top end is fixed.
• Weights are hung on other end of the spring. These are called load.
• As load is increased, the spring is stretched and its length increases.
• When the load is removed, the spring returns to its original length. This is called elastic change.
• When the load is increased in regular steps the length of the spring also increases simultaneously.
• If the load is increased greatly, the spring will change its shape permanently.

Q.5: Define spring? Explain the extension of spring?
Ans: SPRING:
Springs are designed to stretch a long way when force is applied, therefore it is easy to measure changes in their lengths.

EXTENSION OF SPRINGS:

"The length of spring increases as the force (load) increases. This increase in length of spring is known as extension."

Hence,

Length of stretched spring = Original length + Extension

EXPERIMENT FOR STRETCHING SPRINGS OR EXTENSION OF SPRINGS:

• Let’s carry out an experiment to stretch a spring of original length 20 cm.
• The given table shows recorded result of this experiment.
• The first column shows the increase in load in regular steps.
• Second column shows the increase in length of stretched spring.
• Third column shows the value of extension, due to change in length in each step.
  
  

Table for load and extension

Load (N)	Length (cm)	Extension (cm)
0.0	20	0.0
2.0	21	1.0
4.0	22	2.0
6.0	23	3.0
8.0	24	4.0
10	25	5.0
12	26	6.0
14	28	8.0
16	30	10

The above table shows that the spring stretches as the load on it increases.

Graph:

Dependence of extension on the load is shown in the given graph. We can see that the graph has two parts.

• At first, the graph slopes up steadily. This shows that the extension increases in equal steps as the load increases. This behaviour can also be observed in the above table.
• Then the graph bends. This happens when the load is greater enough to damage the spring permanently. As a result the spring will not return to its original length.

Q.6: State and explain Hooke's law?
Ans: HOOKE'S LAW:
Robert Hooke, an English scientist first described the mathematical pattern of stretching a spring. He observed the dependence of displacement or size of the deformation upon the deforming force or load.
Hooke's law states that:

"Within elastic limit, the displacement produced in the spring is directly proportional to the force applied."

In other words,
Hooke’s Law state that the extension in spring is proportional to the load applied to it, provided the limit of elasticity is not exceeded.

Mathematically:
If ‘F’ is the applied force and ‘x’ is the displacement (extension) in the spring then the equation for Hooke's law may be written as:

F ∝ x

or F = kx ....... (i)

Where, k is spring constant (stiffness of spring).

Explanation:

• Hooke's law is applicable to all kinds of deformation and all types of matter i.e., solids, liquids or gases within certain limit. Such limit is called elastic limit. This limit tells the maximum force or stress that can be safely applied on a body without causing permanent deformation in its length, volume or shape.
• In other words,  elastic limit is a limit within which a body recovers its original length, volume or shape after the deforming force is removed. Beyond this limit spring deforms permanently.

Graph:
An extension against load graph is a straight line up to the limit of proportionality.

Q.7: Why was Robert Hooke interested in springs for his experiment?
Ans: Robert Hooke a scientist and inventor was interested in springs for two reasons.

1. Spring are useful in making balances. Hooke wanted to make a very sensitive and accurate weight machine or balance.
2. He also realized that a spiral spring could be used to control a clock or wrist watch.

Q.8: Give young's modulus of the following materials: Brass, Copper, Mild steel, Plastic and Rubber?
Ans: Young’s Modulus Of Given Materials:

Material	Young’s Modulus (in GPa)
Brass	91
Copper	120
Mild steel	210
Plastic	2
Rubber	0.02
Where 1 GPa = 109 Pa

Q.9: Define and explain pressure? Calculate the pressure using formula P = F/A.
Ans: PRESSURE:
Pressure is defined as:

"The force acting normally per unit area on the surface of a body is called pressure."

OR

"The quantity that depends upon the force and increases with decrease in the area on which force is acting is called pressure."

Examples:

• Press a pencil from its ends between the palms. The palm pressing the tip feels much more pain than the palm pressing its blunt end.
• We can push a drawing pin into a wooden board by pressing it by our thumb. It is because the force we apply on the drawing pin is confined just at a very small area under its sharp tip. A drawing pin with a blunt tip would be very difficult to push into the board due to the large area of its tip.
• When force is exerted on area, this is known as pressure, e.g. A hammer hits a nail, driving the nail downwards into a piece of wood.

Explanation:
In these examples, we find that the effectiveness of a small force is increased if the effective area of the force is reduced.
The area of the tip of pencil or that of the nail is very small and hence increases the effectiveness of the force. Thus, Pressure is greater when a large force acts on small area.

Calculation Of Pressure:
Formula:
If F is the magnitude of a force exerted perpendicular to a given surface of area A, then the pressure P equals to the force divided by the area:
Thus,

Nature:
It is a scalar quantity, because pressure acts in all directions. It has magnitude only.

Unit:
PASCAL (S.I Unit):
As the force is measured in newtons (N) and area in square meters (m²).
Therefore in SI system unit of pressure is newton per square meter (Nm^-2). It is also known as Pascal (Pa).

1 Pa = 1 Nm^-2

ATMOSPHERE:
The pressure exerted by the air molecule at sea level is measured in atmosphere.
Where,

1 atmosphere = 1.013 x 10^-2) Pascal

1 atm = 1.013 x 10^-2) Pa

Q.10: Give Reasons:
a. Why an acrobat does not hurt when he lied down on the bed of nails?
Ans: There is no miracle in this trick. We know that pressure is defined as force per unit area. If we step up on a nail, the entire body weight exerts more pressure because the area of nail tip is very small. In case of bed nails, the pressure exerted by weight of body is distributed on the hundreds or thousands of nails lying close to each other. Thus, net pressure on a nail is very small. Hence, an acrobat does not hurt when he lied down on the bed of nails.

b. Explain why foot ball shoes have spikes or studs?
Ans: The pressure under the studs on the soles of football shoes is high enough to sink into the ground, which gives extra grip. Therefore, studs prevent a player from slipping on the grass and help to run faster and change direction quickly without slipping.

c. Why do ice skates have blades?
Ans: Ice skates have blades in the part that is in contact with ice. Therefore the skater's weight is concentrated on a small area. The effect of this high pressure melts ice just below the blades. This gives the thin film of water, which provide lubrication for the skate to skim over the ice. As the skate moves on, the water re-freezes. On very cold days, the pressure may not be enough to melt the ice, and skating is impossible.

d. Why do elephants have broad soles?
Ans: An elephant has broad soles to reduce the pressure exerted on the ground. They have broad feet in proportion to their size, to distribute the weight better.

e. Why does the school bag have broad shoulder straps/pads?
Ans: Wide shoulder pads of school bag reduce pressure on the student's shoulder. These broad shoulder straps are more helpful to distribute the weight of the bag across all over the shoulders. It avoids the weight of concentrating on a particular area.

Q.11: Define fluid? Also describe pressure in fluids?
Ans: FLUIDS:

"A fluid is a collection of molecules that are randomly arranged and held together by weak cohesive forces and by forces exerted by the walls of a container. Both liquids and gases are fluids."

PRESSURE IN FLUIDS:

"The pressure exerted by fluids is known as fluid pressure. It acts in all directions."

This is because the molecules of fluids move around in all directions, causing pressure on every surface they collide with.
Example:
A swimmer in swimming pool experience the pressure by water which pushes the swimmer from all sides. The arrows represent the direction and magnitude of the forces exerted at various points on the swimmer. It shows that the net underneath force is larger due to greater depth, giving a net upward or buoyant force that is balanced by the weight of the swimmer.

Q.12: Describe the factors that affects the pressure?
Ans: FACTORS AFFECTING PRESSURE:
i) Depth:
Pressure P is proportional to the depth, the deeper one dives into water, greater will be the pressure. Twice the depth means twice the pressure.

ii) Density Of Material:
Similarly, pressure also depends upon the density of the material. If a material is five times denser than water, the pressure will be five times greater.

Relation Between Pressure, Depth And Density of Material:
Mathematically,
At a depth 'd' in a fluid of density 'ρ', the pressure 'p' can be written as:

Pressure = depth x density x acceleration due to gravity

p = dρg ..............(iii)

Thus, The pressure in a fluid is greater with large depth, and high density.

Q.13: What is Density?
Ans: DENSITY:
The term density of a substance is defined as mass of substance (m) per unit volume (V). It is denoted by Greek letter ρ (rho).

ρ = m / v

Density is characteristic property of any pure substance. Density tells us that the matter is packed tightly together. If something is packed very tightly together it is considered to be “dense”. More dense sinks and pushes up less dense. 
Objects made of a particular pure substance such as pure Gold can have any size or mass but its density will be same for each. In accordance with the above equation mass of a substance can be expressed as

m = ρV

S.I Unit Of Density:
The S.I unit for density is kg/m³ or kgm^-3. Sometimes density of substances is given in gm/cm³.

Example:
The density of Aluminum is 2.70 gm/cm³ which is equal to 2700 Kg/m³.

Q.14: What are hydraulic machines?
Ans: HYDRAULIC MACHINES:
The machine in which force is transmitted by liquids under pressure is known as hydraulic machine. It also work on the principals of fluid pressure. By the application of relatively small force they produce a greater force.
Example:
Hydraulic breaks are used almost in all vehicles. They cause a relatively small force from the driver's foot to be multiplied to produce a greater force, which acts equally on all four brake pads. Thus a hydraulic machine works on Pascal's law.

Q.15: State and explain Pascal's Law?
Ans: PASCAL'S LAW:
This law may be stated as:

"The pressure applied externally at any point of a liquid enclosed in a container is transmitted equally to all parts of the liquid in container."

Explanation:
The liquid pressure at the surface of the liquid increases when an external force is applied on the surface of the liquid. The increase in the liquid’s pressure is transmitted equally in all directions, in similar way it is transmitted equally to the walls of the container in which it is filled. This result leads to a law known as Pascal's law.

Example (Demonstration Of Pascal's Law):
It can be demonstrated with the help of a water filled glass vessel having holes around its surface. When we apply force through the piston the water rushes out of the holes with the same pressure.
The force applied on the piston exerts pressure on water. This pressure is transmitted equally throughout the liquid in all directions. In general, this law holds good for fluids both for liquids as well as gases.

Uses Of Pascal's law:

• A hydraulic machine works on this principle
• Hydraulic brakes
• Car lifts
• Hydraulic jacks
• Forklifts and other machines make use of this principle

Q.16: Describe the working of a hydraulic press?
Ans: HYDRAULIC PRESS:
A hydraulic press is made of two pistons connected by a liquid-filled pipe.
A force of magnitude F₁ is applied to a small piston of surface area A₁. The pressure is transmitted through an incompressible liquid to a larger piston of surface area A₂. Because the pressure must be the same on both sides.

Therefore, the force F₂ is greater than the force F₁ by a factor ^A₂/_A1.
By designing a hydraulic press with appropriate areas A₁ and A₂, a large output force can be applied by means of a small input force.
Each side of this equation is the work done by the force. Thus, the work done by F₁ on the input piston equals to the work done by F₂ on the output piston. Thus the principle of conservation of energy applies in the hydraulic press.

Biology For Class X - Chapter No. 7 - Man And His Environment - Notes By FAW Group Of Education

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CHAPTER 7: MAN AND HIS ENVIRONMENT

Notes By FAW Group Of Education

For Educational News update like our FACEBOOK Page and YOUTUBE Channel:
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UNIT 07. INTRODUCTION TO SCRATCH - MCQs - Computer Science For Class X

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Computer Science For Class X
Unit 04: Control Structure
Multiple Choice Questions And Fill In The Blanks

By Mrs. Ayesha Arif
Vice Principal
(Jauhar Progressive School)

Multiple Choice Questions (MCQs)

A. ENCIRCLE THE CORRECT ANSWER:
i) The feature of Scratch is:
a) It is a visual
b) Its free forever
c) No need to remember codes
d) All of above ✓

ii) In Scratch, the character which moves on the Stage is called a:
a) Sprite ✓
b) Command
c) Script
d) Event

iii) Repeat 10, forever and if ... then codes are available in:
a) Motion
b) Control ✓
c) Look
d) Sensing

iv) The Looks of Sprite can be changed by using:
a) Backdrop Tab
b) Costume Tab ✓
c) Script Tab
d) Control Tab

v) A Scratch program is at least made up with:
a) Many Sprites
b) One Sprite and Code
c) One Sprite ✓
d) One Sprite and Backdrop

vi) To change the position of Sprite on screen, we use:
a) Coordinates ✓
b) Stage Information
c) Command Pallets
d) Costume Tab

vii) This can be found under _____.

a) Look
b) Motion ✓
c) Sound
d) Control

viii) Turn command, turns Sprite to specified:
a) Coordinate
b) Degree ✓
c) Steps
d) Second

ix) This command is available in:

a) Event
b) Motion
c) Control ✓
d) Looks

x) In the given picture identify the x and y coordinates (positions) of Point - A.

a) x = 100, y = -100 ✓
b) x = -100, y = 100
c) x = 100, y = 100
d) x = -100, y = -100

HINT:

Fill In The Blanks:
1. Scratch is a programming language.
2. Scratch program includes animations and games.
3. From scratch programming, we can create interactive stories, games, animation, music, art, and presentations.
4. There are two basic components of a Scratch program; Sprite and Script.
5. We can use Scratch online and offline.
6. In Scratch Environment, the Stage is where you see your stories, games, and animations come to life.
7. In Scratch Environment, the Script is the set of stepwise instructions that users give to the sprite to do a particular task.
8. In Scratch Environment, Backdrop is the background that the user can add on stage.
9. Scratch blocks are organized into different categories in the left columns.
10. Motion block has instructions to make the Sprite move, such as number of steps to take, direction of motion, etc.,
11. Event is used to trigger code at a specific time or action.
12. Sound is used to play different sounds.
13. Looks is used to change the appearance of the Sprite and Backdrop.
14. Control is used to control the action on the stage.
15. Sensing is used to sense any specific happening.
16. Backdrop is the background of stage.
17. Costume is the appearance of Sprite.
18. Scratch has a 2D coordinate system: "x position” and "y position".
19. User can choose Backdrop or Sprite from library, Paint New, Upload from File and Capture from Camera.
20. Variables can be created through Data Pallet.

Source: Special Thanks To Sir Syed Arif Ali

UNIT 07. INTRODUCTION TO SCRATCH - Text Book Exercise And Question Answers - Computer Science For Class X

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Computer Science For Class X
Unit 07: Introduction To Scratch
Question Answers

By Mrs. Ayesha Arif
Vice Principal
(Jauhar Progressive School)

Q.1: What is scratch ? Give some of its advantages.
Ans: SCRATCH:
Scratch is a visual programming language. It is very easy to create programs in scratch. It allows students to create their own interactive stories, games and animations, etc. This programming tool was developed by Massachusetts Institute of Technology (MIT) Media Lab . It is free to use and distribute and it will remain free forever.

ADVANTAGES OF SCRATCH:
Scratch can be used for multiple purposes:

• Interactive stories ,games ,animations, music, art and presentations can be created simply by dragging and dropping colour blocks.
• While working with scratch students learn important mathematical and computing concepts that improve their creative thinking and logical reasoning problem solving.
• As students design Scratch projects, they learn to think creatively, reason systematically, and work collaboratively.
• kids can create animation easily by using scratch.
• Teens can develop games.
• Teachers and students can use it to create effective education tools such as math quiz, science simulation and educational videos.
• It is so easy to use that anyone can master it within short period of time.

Q.2: Write down the procedure and steps to download and install scratch offline and online.
Ans: Downloading And Installing Scratch Offline:

• Scratch can be downloaded or installed on computer or any android device to work offline.
• The latest version can be downloaded for Windows 10 or Android 6 or the later versions.
• Scratch 2.0 is a good version that can work on most of the computers and can be downloaded from website:
  
  http:// scratch.mit.edu/download/scratch 2

OFFLINE INSTALLATION:
Installation of scratch is very easy. The instructions for installation of Scratch 2.0 are given below:

• To begin scratch Offline Editor for Windows needs to be installed on computer.
• After down loading we need to just run the executable (.exe) file.
• The first screen will appear which will ask the location where we want to install the Scratch.
• It will also ask about the shortcuts to create. We need to just continue with default options.
• This will initiate the installation process and after installation, Scratch will be ready to use.

SCRATCH ONLINE INSTALLATION:

• Scratch can also be used online by simply loading its editor in our web- browser which is available at:
  
  https:// scratch.mit.edu/projects /editor
• After loading the editor, it will function just like the offline editor.
  We can also create our account on Scratch. This will enable us to save our projects online.

Q.3: What do you know about Sprite and script?
Ans: SPRITE:
The sprites are the images of cartoons, characters or objects that we add in our project. We can have multiple sprites in our project but at least one sprite is always needed for the project. Cat is the default sprite in scratch.

SCRIPT:
To create a game, interactive story, animation or art work in scratch, We must add visual instructions to tell a sprite exactly what to do. The scripts are instructions that make sprites perform a task. Each sprite in a scratch project has an area for scripts through which it is programmed. Clicking on a script's thumbnail in the sprite pane will bring up the script area of that sprite.

OR

The scripts are the visual instructions to tell a sprite what to exactly do. In short, Scripts are the instructions in a visual form that make a sprite perform a specific task.

Q.4: Write in detail about the different components of scratch editor.
The scratch editor has the following components:

1. Stage or stage preview
2. Script area
3. Sprite list
4. Backdrop
5. Script block
6. Script tab
7. Costume tab
8. Sound tab
9. Cursor tool

1. Stage or stage preview:

• It is the main working area where the spite moves and performs actions according to the given instructions.
• Here we can immediately see the output of our codes.
• The project runs physically in this window.
• It is divided into X (horizontal) and Y (Vertical) co ordinates. The coordinates are displayed at the bottom right corner of the stage.
• These coordinates indicate the position of the sprite on stage.

2. Script area:

• This is the area where the code or program is seen.
• Blocks from the palette can be dragged to this area and create scripts by placing them together.
• Script is the set of step wise instructions that we give to the Sprite to do a particular task.
• Each sprite has its own script area.

3. Sprite list:

• It displays the thumbnails of all the sprites available in a project.
• The blue information icon can be clicked on any sprite to change its name or behavior.

4. Back drop:

• A backdrop is a background that can be added to the stage.
• By default, no backdrop is added in a project.
• The look of the stage can be altered by adding a backdrop.

5. Script Block:

• Script area has three different tabs.
• A tab is a small area that contains similar commands or options.

6. Script Tab (code tab in scratch 3):

• This area can be considered as tool box.
• On clicking this tab block palette is opened.
• The sprites are used to give commands.
• A command is an instruction to do specific task.
• In scratch these commands are shown in the form of Code Blocks in the Block Palette.
• The block palette consist of every block of instruction that is built into scratch.
• The commands regarding a specific task are joined together in different blocks.
• Each block has associated colour that differentiate different commands.
• Some blocks and their purposes are as follows:
  
  1. Motion: These codes are used to move Sprite on the stage.
  2. Event: Event trigger specific codes at a particular time or action.
  3. Sound: is used to play different sounds.
  4. Looks: These codes are used to change the appearance of sprite and backdrop.
  5. Control: These codes are used to control the action on the stage.
  6. Sensing: These codes are used to sense any specific happening.
  7. Data: These are used to initialize variables and list.
  8. Pen: This used to draw lines, rectangles and other shapes.
  9. Arithmetic: This shows the available logical and relational operators.

7. Costume tab:

• By clicking on the "Costumes" tab the appearance of a sprite can also be changed into the desired costume of choice.
• It can also be changed by using blocks to select the sprite’s costume.
• New costumes for the sprite can be Imported, Created, and Edited in the Scratch Paint Editor.

8. Sound Tab:

• Sound is an optional field. We can have sprites with no sounds.
• Some sprites additionally have at least one sound.
• The sounds tab allows to add, delete, and edit sounds.
• Sounds can be played in the sound editor or with blocks that play a specific sound.

9. Cursor tool:

• Cursor Tool is located on the right top of the editor.
• It includes five options; Duplicate, Delete, Grow, Shrink and Help.
• To Duplicate a sprite, just click on the stamp and then on the Sprite.
• Same is applicable on Delete, Grow and Shrink.

Q.5: Name the blocks of script tab along with their purpose and examples.
Ans: BLOCKS WITH THEIR PURPOSES AND EXAMPLES:

BLOCK	PURPOSE	EXAMPLES
Motion	These codes are used to move the Sprite on stage.	Move; Turn; go to x,y; if on edge, bounce;
Events	Events triggers specific code at a particular time or action.	When flag is clicked; when space key is pressed, when backdrop switches to.
Sound	This is used to play sound.	Play sound; play drum 1 for 0.25 beats, play note 60 for 0.5 beats.
Looks	These codes are used to change the appearance of the sprite and Backdrop.	Say; think, switch costume to and switch Backdrop to are some commonly used codes.
Control	These codes control the actions on the stage.	Wait 1 sec, repeat 10, forever, if then.
Sensing	These codes sense any specific happening.	Touching mouse pointer, touching colour, ask and wait.
Data	These are used to initializes variables and lists.	Variable and lists.
Pen	This is used to draw rectangles ,lines and other shapes.	Pen up, pen down, pen colour.
Operators	This shows available arithmetic, logical and relational operators.	+; -; *; /; <; >; =

Q.6: What points should be kept in mind before developing a project? And What steps are generally taken to develop a simple program in scratch?
Ans: POINTS TO BE KEPT IN MIND BEFORE DEVELOPING A PROJECT:
The following points should be kept in mind before developing a project:
Most of the Scratch Programs contain Sprites, Backdrops and Code Blocks.
Every Sprite in a program has a separate Code Block which controls its actions.
We can develop programs for different logics like storytelling, sprite animation, simple game and others.

STEPS TO DEVELOP A SIMPLE PROGRAM:
Following are the general steps to develop a program in scratch:
Open Scratch Editor

• Events:
  From Events Option in Script, drag and drop on script area.
  
  
• Control:
  From Control Option, drag forever and drop on script area. Inside the forever block, drag and drop the illustrated commands and change values accordingly. Colors will help you to find the option. After completing the codes blocks, Play (Run) and Stop the program.
  
  
  
  
  
• Playing and Stopping the Animation/Program:
  To start your program or to test your code click the Green flag icon located above the Stage panel. To stop your program, click the Red Stop icon.
  
  
  
  
  
• Coordinates On Scratch Stage:
  Scratch has two dimensional (2D) coordinate system; "X" position which and "Y" position to determines the location of a sprite on the stage. The "X position value determine the horizontal location of the sprite and "Y" position value determines the vertical location.
  The screen in scratch is a 480 x 360 rectangle. The "X" position can range from -240 to 240, where -240 is the leftmost a sprite can be and 240 is the rightmost. "Y" position can range from 180 to -180, where 180 is the topmost it can be and -180 is the bottom-most it can be.
  
  
  
  
  

Q.7: Explain this program of scratch? Or What is the Output of this program?

Ans: Program Explanation:

• When ⚐ clicked: It is an event. It runs the program when flag is clicked.
• Forever: block keeps repeating the commands for infinite time.
• Moves 20 steps: Goes to next costume. Moves sprite 20 steps forward.
• Wait 0.5 seconds: Makes sprite wait for (0.5) seconds.
• if on edge, bounce: When sprite touches corner. it returns back.
• set rotation style [left-right]: This keeps turning the direction left-right.

OUTPUT:

Q.8: List some important commands in scratch with their purpose.
Ans: SOME IMPORTANT COMMANDS IN SCRATCH:
Some important commands which are usually used to developed simple programs are:

B. RESPOND THE FOLLOWING:

1. Explain the following:
i. Script
ii. Sprite
iii. Backdrop
Ans: For Script and Sprite see above Q.2 and
For Backdrop see above Q.3.

2. State the difference between repeat 10 and forever commands.
Ans: Difference Between Repeat 10 and Forever Commands.

• Forever: Forever command keeps on repeating the command for infinite times.
• Repeat 10: While repeat 10 command repeats the command only for 10 times.

3. Write the use of the following codes: forever, wait, say, play sound, go to x, y?
Ans: Codes With Their Uses:

S.NO.	Words
forever	Keep repeating the code blocks for infinite times
wait	Makes sprite waits for specific seconds
Play sound	Used to play specific sound
say	Commands the spite to say words or phrase in a specific seconds
Go to x, y	Make the sprite move to specific location at x or y coordinates (position on stage).

4. What is the difference between using scratch online and offline?
Ans: Difference Between Using Scratch Online And Offline:
There is a difference between using scratch online and offline.
Scratch Online:

• In Online scratch we can communicate with the community and see shared projects of others.
• Online we can also share our own projects.
• Discussions and chats can also be done while using on line scratch.

Scratch Offline:

• While using scratch offline we can only make projects and upload or download them to usb's.

10. How are colours helpful for the user?
The colours in script tab are helpful for the user in the following ways:

1. The colours prevent the user from getting confused.
2. The colours code makes it easier for the user to use different commands.
3. When there are too many scripts in one sprite the colours make it easier to find them.

UNIT 06. DIGITAL LOGIC AND DESIGN - MCQs - Computer Science For Class X

GO TO INDEX

Computer Science For Class X
Unit 04: Control Structure
Multiple Choice Questions And Fill In The Blanks

By Mrs. Ayesha Arif
Vice Principal
(Jauhar Progressive School)

Multiple Choice Questions (MCQs)

A. ENCIRCLE THE CORRECT ANSWER:
1. The Universal gate is:
a) NAND gate ✓
b) AND Gate
c) OR Gate
d) None of these

2. The _________ is inverter.
a) AND
b) OR Gate
c) NOT ✓
d) None of these

3. In Boolean Algebra, the bar sign (-) indicates __________.
a) OR Operation
b) NOR Operation
c) NOT Operation ✓
d) Both b and c

4. The Boolean Algebra is used for _____________.
a) Creating Circuits
b) Apply 12 rules of Boolean
c) Simplify the Boolean expression ✓
d) Differentiate the gates

5. With the combination of three variables, how many outputs are expected altogether?
a) Three
b) Six
c) Eight ✓
d) Nine

6. A + A = A is a ________ rule of Boolean Algebra.
a) 3^rd
b) 6^th
c) 5^th ✓
d) 7^th

7. A.A = 0 is a _________ rule of Boolean Algebra.
a) 1^st
b) 8^th ✓
c) 6^th
d) 10^th

8. Simplify form of Boolean expression of ABC + ABC + AB is _________.
a) A
b) B ✓
c) C
d) B

9 .Simplify form of Boolean expression of ABC+ABC is:
a) AC
b) BC ✓
c) B
d) A

10. Boolean expression of the given circuit is:

a) A + B
b) B.A
c) A.B
d) A.B ✓

FILL IN THE BLANKS:
1. Data Representation refers to the form in which data is stored, processed, and transmitted.
2. Digital devices such as smart phones, iPods, and computers store data in digital formats that can be handled by electronic circuitry.
3. Logic Gates are the electronic circuits in a digital system.
4. Logical Gates perform logical operations like AND, OR, NOT, NAND, NOR etc.
5. The logic gate is the basic unit of digital logic circuits.
6. There are mainly three basic gates AND, OR, and NOT.
7. The basic logical gates perform AND, OR, and NOT operations in the digital system.
8. An AND gate is a digital circuit that has two or more inputs and a single output AND gate operates on logical multiplication rules.
9. Boolean Expression of AND gate: Y=A.B
10. An OR gate is a digital circuit that has two or more inputs and a single output.
11. OR gate operates on logical Addition rules.
12. Boolean expression of OR gate is Y=A+B.
13. A NOT gate is a digital circuit that has a single input and a single output.
14. NOT gate is also known as INVERTER.
15. Universal Gates are logic gates.
16. Universal Gates are capable of implementing any Boolean function without requiring any other type of gate.
17. There are two types of universal gates.
18. A NAND Gate could be construct by connecting a NOT Gate at the Output terminal of the AND Gate.
19. Boolean expression of NAND gate is Y= (A.B)'or Y = AB.
20. A NOR Gate could construct by connecting a NOT Gate at the output terminal of the OR Gate.
21. The Boolean expression of NOR gate is Y = (A + B)' or Y = A + B.
22. The Boolean arithmetic rules are pre-defined rules that help to simplify the logical expression.
23. There are 12 Boolean algebra rules.



Source: Special Thanks To Sir Syed Arif Ali