1. Hooke’s Law Experiment
Introduction
Hook’s Law is used in designing devices that uses springs. If we have to design a kitchen scale or door
locks we have to determine what force is required to produce the required displacement and also it
should return to its original position when the load is removed. Thus, hooke’s law is vital in such
scenario.
Theory
Hookes Law states that for relatively small deformationsofanobject,thedisplacementor size of the
deformationisdirectlyproportionaltothedeforming force or load. Under theseconditionstheobjectreturns
to its original shape and size upon removaloftheload. It can be written as
Fs = -ks
whereFs is the tension in a stretched spring and s is the spring's displacement from its unstretched
position. k is the elastic constant, or "spring constant."
Common Types of Spring
1. Tension Spring
2. Compression Spring
Tension Spring
Extension springs, also known as a tension spring, are helically wound coils, wrapped tightly together to
create tension. Extension springs usually have hooks, loops, or end coils that are pulled out and formed
from each end of the body.
The function of an extension spring is to provide retracting force when the spring is pulled apart from its
original length.
Commons use
Trampoline

2. A trampoline uses many extension springs to create the bouncing effect. Every time someone jumps on
the trampoline, the extension springs are pulled apart and force is exerted. This makes the extension
spring want to go back to its original length, thus giving the inertia to fly into the air.
Procedure
1. Push the crosshead above until and unless the spring becomes slack.
2. Set the cell reading to zero and note the position of the double-edged pointer
3. Release the cross head and let it come to rest so that the weight and the tension becomes
equal.
4. Tap the equipment so that any stoppage due to friction is released and the equipment comes to
rest at the position given in point 3.
5. Next note the reading of the scale pointer.
6. Turn the screw on the cross head so it stretches the spring 2 mm (0.002m) and take the reading
from the Load cell.
7. Repeat in 2 mm (0.002 m) steps, until you reach the end of the Crosshead travel.
Tips:
The scale has two edges. Look across both of these to reduce the parallax error.
To remove the pretension in the spring (if it not appropriate for your course) pull the spring by
the loops until the coils no when the spring is relaxed.

3. Conduct the experiment and note down its reading
Observ. Scale
No Distance Reading
(mm) (N)
1 132 3
2 134 3.5
3 136 4
4 138 4.6
5 140 5.2
6 142 5.7
7 144 6.2
8 146 6.7
9 148 7.2
10 150 7.7
11 152 8.2
12 154 8.7
13 156 9.2
14 158 9.9
15 160 10.6
16 162 10.9
17 164 11.4
18 166 12
19 168 12.6
20 170 13.2
21 172 13.6
22 174 14
23 176 14.6
24 178 15.2

4. Draw the best fit curve (line). What is the trend that you observe? Linear.
Tension Vs Displacement
18
16 y = 0.529x + 2.456
14
Force Recorded (N)
12
10
8
Series2
6
Linear (Series2)
4
2
0
132
136
140
144
148
152
156
160
164
168
172
176
Scale Reading (mm)
Determine the spring constant. Using k = (y2-y1)/(x2-x1)
K=0.5298 N/mm
Determine the y-intercept. What does this indicate?
That the spring is already under tension by 2.4569N
At what scale reading would the spring have no load?
Displacement at no Load = 132 – 2.4569/0.5298 = 127.3626 mm
Draw the free body diagram of tension spring apparatus, demonstrating all the forces acting
on it if the Load Cell shows a reading of 5 N, when it has reached an equilibrium state.
Drawn on back of page 6T

5. Compression
Practical Example: Pogo stick
A pogo stick is a toy that works as an exercising tool without children realizing their fun is
actually healthy. A child uses his legs, abdomen and arms to operate a pogo stick with repeated
movement, exercising each muscle. A pogo stick is a simple machine called a spring that uses
the weight of the child pressing down on the spring to cause the spring to push the child up into
the air.
Procedure
1. Take up the slack in the spring by using the screw on the crosshead until the load cell pointer
just begins to move
2. Set the load cell to zero and note the position of the double-edged pointer.
3. Turn the screw on the crosshead so it compresses the spring 2 mm (0.002m) and take a reading
from the Load cell.
4. Repeat in 2mm (0.002 m) steps until you reach the end of the crosshead travel or when the
spring is fully compressed.
Tips:
The scale has two edges. Look across both of these to reduce the parallax error.
Draw the free body diagram showing all the forces acting on the apparatus when the spring
balance is showing the reading of 3 N.
Diagram drawn on back of page 7T.

6. Conduct the experiment and note down the observations.
Observation Scale Reading on Scale Reading – Compression
number Compression (mm) Intial Reading (mm) force Recorded(N)
1 55 0 0
2 53 -2 -2
3 51 -4 -3
4 49 -6 -4.1
5 47 -8 -5.3
6 45 -10 -6.7
7 43 -12 -7.9
8 41 -14 -9
9 39 -16 -10.1
10 37 -18 -11.4
11 35 -20 -12.4
12 33 -22 -13.8
13 31 -24 -15
14 29 -26 -16.2
15 27 -28 -17.4
16 25 -30 -18.4
17 23 -32 -19.6
18 21 -34 -20.6

7. Draw the best fit curve (line). What is the trend that you observe? Linear.
Compression Vs Displacement
Displacement (mm)
-28
-34
-32
-30
-26
-24
-22
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
0
y = 1.194x - 22.06
-5
Force Generated (N)
-10
Series2
Linear (Series2)
-15
-20
-25
Calculate k of the above experiment
K = 1.1704 N / mm

8. Other Questions
The turning total length of the bolt thread is 80 mm. Count the number of revolutions a nut would take
to reach from top to bottom.
What is the pitch of the bolt
How many turns would we have to provide if we have to compress the spring from 8mm to 6 mm.