Physics Practicals - For Class IX and X (Science Group) - PRACTICAL 04(X) 05(IX): Find the Specific Gravity of a body heavier than water by Archimedes principle.

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PRACTICAL 04(X) 05(IX):

Find the Specific Gravity of a body heavier than water by Archimedes principle.

APPARATUS:

• Physical balance
• Weight box
• Insoluble solid
• Beaker
• Water
• Bench
• Thread

THEORY:
ARCHIMEDES'S PRINCIPLE:
When a body is partially or wholly immersed in a liquid, due to upthrust it appears to lose some of its weight. The loss in weight of !he body is equal to the weigh of the liquid displaced.

SPECIFIC GRAVITY OR RELATIVE DENSITY:
It is the ratio of density of the substance to the density of water at 4 °C.

METHOD: (2 Marks)

• Adjust the balance with the help of adjusting and leveling screw.
• Suspend the bob in left-hand pan with thread.
• Find the weight of bob in air.
• Place a wooden bridge across left pan and place a beaker containing water.
• Find Weight of bob in water such that it does not touches the side wall of beaker. Bob should remain in water when beam is raised.

OBSERVATIONS: (5 Marks)

OBS.	WEIGHT OF SOLID IN AIR W1 (gm-wt)	WEIGHT OF SOLID IN WATER W2 (gm-wt)	LOSS OF WEIGHT OF SOLID IN WATER W1 - W2 (gm-wt)

CALCULATIONS:
FORMULA (1 Mark)

Specific gravity = ----------------- = --------------------

RESULT:
Specific gravity of given solid is found to be = ----------

FIGURE: (2 Mark)

PRECAUTIONS:

• Physical balance must be adjusted.
• Pan must not touch the wooden bench.
• Use foreceps to take weights from the weight box.

Special Thanks to Sir Sajjad Akber Chandio

Physics Practicals - For Class IX (Science Group) PRACTICAL 04: To study the relation between "Load" and "Extension" of a helical spring by drawing a Graph.

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PRACTICAL 04:

To study the relation between "Load" and "Extension" of a helical spring by drawing a Graph.

APPARATUS:

• Elastic spring (Helical spring)
• Hooke's Law stand with scale
• Slotted weights
• Pointer

THEORY:
ELASTICITY:
The property of a body to regain its original shape when deforming force have been removed called elasticity.

STRESS:
Recovering force per unit area called stress. Its units is Newton per square meter (N/m²).

STRAIN:
Fractional changes in length, volume or shape called strain. Change in length per unit original length is called linear stress.

HOOKE'S LAW:
Within elastic limits stress is directly proportional to strain.

Stress ∝ Strain

^Stress / _Strain = Constant

Within elastic limit the applied force (load) is directly proportional to extension.

 Extension (F) ∝ Load (l)

F = kl

^F / _l = k

METHOD: (1.5 MARKS)

• Place iron stand on horizontal surface and suspend spring with the help of hanger of slotted weights and adjust pointer at zero.
• Add one slotted weight (of 20 gm-wt) in the hanger.
• Note down the position of pointer on the scale.
• Take five observation by increasing the load step by step each time note down the position of pointer on the scale when pointer is at rest.
• Calculate the extension of each load.
• Calculate the ratio of F/l for each observation.

OBSERVATION:

S.No.	Applied Force (F) load (gm-wt)	Pointer Reading (l) extension (cm)	F / l (gm-wt / cm)
1,
2.
3.
4.
5.

FIGURE: (1 MARKS)

GRAPH: (2 MARKS)

• Draw x and y-axis on the graph paper.
• Take load 'F' on x-axis and extension 'l' on y-axis.
• Supply suitable scale. Plot values of 'F' and 'l' from observation column.
• Draw line, which join the points.

(Note: This is a sample graph with assuming readings. The graph should be in a straight line if correct readings are obtained.)

RESULT: (0.5 MARKS)
Since ratio between "F" and :l" is constant and graph between F and l is a straight line therefore load and extensions are directly proportional to each other.

PRECAUTIONS:

• Stand must be vertical.
• Turns of the spring should not overlap each other.
• Pointer reading must be taken by keeping the eye at its level.

Special Thanks to Sir Sajjad Akber Chandio

Physics Practicals - For Class IX (Science Group) PRACTICAL 03: To verify the Principle of Moment by using a meter rod balanced on a wedge.

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PRACTICAL 03:

To verify the Principle of Moment by using a meter rod balanced on a wedge.

APPARATUS:

• Metallic stand with sharp wedges block
• Uniform meter scale
• Weights
• Thread Or Hooks

THEORY:
Torque or moment of force is the measuring effect of force produced in a body about certain axis.

Torque = Force x Force arm

T = F x d

Its unit is Newton-meter. Anti clock wise torque is positive and clockwise torque is negative.

PRINCIPLE: (1 MARK)
If algebraic sum of all the torque is zero the body is said to be is equilibrium.

MATHEMATICALLY:
Anti clock wise Torque = Clockwise Torque

METHOD: (2 MARK)

• Pivot the meter rod in horizontal position from its mid point.
• With the help of thread loops or hooks suspend two different weights W₁ and W₂ on the right hand side, and W₃ and W₄ on the left hand side of the fulcrum.
• Adjust these weights so that the meter rod is again horizontal.
• Note down the value of W₁, W₂, W₃ and W₄, and their corresponding moment arms d₁, d₂, d₃ and d₄.
• Take these sets of observation by changing weight and their position.
• For each set of observation calculate clockwise and anticlockwise torque.

OBSERVATIONS:

OBS	CLOCKWISE MOMENTS (TORQUES)				ANTICLOCKWISE MOMENTS (TORQUES)
	W1 (gm-wt)	d1 (gm-wt)	W2 (gm-wt)	d2 (gm-wt)	W3 (gm-wt)	d3 (gm-wt)	W4 (gm-wt)	d4 (gm-wt)
1
2
3

CALCULATIONS:

Sum of clock Torque = Sum of anti clock Torque

W₁ X d₁ + W₂ x d₂ = W₃ X d₃ + W₄ x d₄

1. ---------- + ---------- = ---------- + ----------

  ---------- + ---------- = ---------- + ----------

---------- gm wt - cm

2. ---------- + ---------- = ---------- + ----------

  ---------- + ---------- = ---------- + ----------

---------- gm wt - cm

3. ---------- + ---------- = ---------- + ----------

  ---------- + ---------- = ---------- + ----------

---------- gm wt - cm

RESULT:
Since in equilibrium position of meter rod, sum of clockwise moments is equal to the sum of anti clockwise moments therefore principle of moment is verified.

FIGURE: (1.5 MARKS)

MOMENT APPARATUS

PRECAUTIONS:

• Weights must be standard.
• Loops of thread must be small and equal in size.
• In equilibrium position scale must be horizontal.

Special Thanks to Sir Sajjad Akber Chandio

Physics Practicals - For Class IX and X (Science Group) - PRACTICAL 02: Determine the Resultant of two vectors by (Gravesend's apparatus).

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PRACTICAL 02:

• Determine the Resultant of two vectors by (Gravesend's apparatus).

APPARATUS:

• Gravesend's Apparatus i.e:
  i) Vertical drawing board
  ii) Two fixed pulleys (clamped to the top)
• Three sets of 20 gm slotted weights with hanger
• Plane mirror strip
• Drawing paper
• Thumb pin
• Light string about 1 meter long
• Meter Scale
• Geometry box

THEORY:
Those physical quantities, which are completely, specified only when direction is also mentioned along with magnitude and units are known as vector.

RESULTANT VECTOR:
Vectors, which gives combined effect of two or more vectors, called resultant vectors.

TRIANGULAR LAW OF VECTOR ADDITION:
If two vectors represent two sides of the triangle, then third side of triangle in reverse order will be the resultant of the two sides.

PARALLELOGRAM LAW OF VICTOR ADDITIONS:
According to this law the diagonal of parallelogram represents the resultant of two adjacent of the parallelogram.

METHOD: (1 + 1 MARKS)

• Fix drawing paper in the middle of the vector board and place it vertically.
• Adjust the thread, carrying a set of weights at each end, over two pulleys.
• The small thread carrying third set of weights at the center of the first two thread.
• Place plane mirror under one of the thread keeping one eye close and mark two points 'A' and 'B', such that the two points and the image of thread lie exactly under the thread.
• Similarly mark C, D and E, F under other two thread.
• Join A and B, C and D. and E and F and extend them to meet at point O.
• Select suitable scale (10 gm-wt = 1 cm) and draw arcs OP and OQ corresponding to their weights.
• Draw PX and QX parallel to OP and OQ.
• Join P and X and 0 and X.
• OX is the resultant of OP and PX.
• Find magnitude of OX by multiplying its length with the scale.
• Repeat above procedure by using unequal weights and find their resultant.

OBSERVATIONS: (1 + 1 MARKS)

OBS	WEIGHT OF RIGHT HAND SIDE (OP) gm-wt	WEIGHT OF LEFT HAND SIDE (OQ) gm-wt	RESULTANT WEIGHT (OX) gm-wt
1.
2.

FIGURE:

RESULT:
1. The magnitude of the resultant of two equal vectors each of ______ is _______ gm-wt.
2. The magnitude of two unequal vectors of _______ gm-wt and _______ is ______ gm-wt.

PRECAUTIONS:

• Board must be exactly vertical.
• Standard weights must be used.
• Pulleys must be friction less.

Special Thanks to Sir Sajjad Akber Chandio

Physics Practicals - For Class IX (Science Group) - PRACTICAL 01: Determine the Diameter of a small sphere using a Micrometer Screw Gauge and calculate its volume.

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PRACTICAL 01:

Determine the Diameter of a small sphere using a Micrometer Screw Gauge and calculate its volume.

APPARATUS:

• Screw gauge
• Small sphere

THEORY:
Micrometer screw gauge consists of a U - shaped steel frame of a fixed stud and a movable stud, which can move in a hollow cylinder called drum or thimble. It has two scales one is called main scale and other is called circular scale.

LEAST COUNT:
Smallest distance that can be measured by it called least count.

PITCH:
It is the perpendicular distance between the two adjacent threads.

ZERO ERROR:
When two studs of screw gauge are in contact and zero of main scale does not coincide with the zero of the circular scale then screw gauge is said to have zero error.

FORMULA: (1 MARK)
Volume of sphere = ⁴/₃ πr³

METHOD: (2 MARKS)

• Find pitch of screw gauge by giving one rotation to circular scale.
• Calculate least count of screw gauge.
• Remove zero error if present.
• Place the sphere between studs and screw up till thc sphere heId gently. Note main scale reading and circular scale reading at line of reference.
• Multiply circular scale reading and least count to get fractional part.
• Add main scale reading and fractional part to get total diameter.
• Take three readings each time fixing the sphere from a different side.

OBSERVATIONS: (2 MARKS)
Pitch of screw gauge = 1 mm = I/10 cm = 0.1 cm
Least count = Pitch of the screw gauge / No. of circular scale divisions
L.C. = 0.1 / 100 = 0.001 cm

DIAMETER OF SPHERE:

OBS	MAIN SCALE READING (M.S.R) cm	CIRCULAR SCALE READING (C.S.R) div	FRACTIONAL PART F.P. = C.S.R x L.C cm	TOTAL DIAMETER D = M.S.R + F.P cm
	1.2 cm	70 div	70 x 0.001 = 0.07 cm	1.2 + 0.07 = 1.27 cm
1
2
3

CALCULATIONS: (1+4 MARKS)

RESULT:
Mean Diameter of sphere = _____ cm and
Volume of sphere = _____ cm³

FIGURE: (2 MARKS)

PRECAUTIONS:

• If there is zero error then it must be removed.
• Reading must be taken at different points of the spheres.

Special Thanks to Sir Sajjad Akber Chandio