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PRACTICAL 04:
To study the relation between "Load" and "Extension" of a helical spring by drawing a Graph.
- 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
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
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