Required Practical – Hooke’s Law
Hooke’s Law
Aim of practical: Investigating force and extension of a spring.
Risk Assessment: Ensure that the clamp stand is securely fastened to the
table.
Method:
Set up the equipment as shown in the diagram.
The zero should be at the top of the ruler.
2. Adjust the ruler so that it is vertical. The zero on
the scale needs to be at the same height as the
top of the spring.
3. Attach the splint securely to the bottom of the
spring. Make sure that the splint is horizontal
and that it rests against the scale of the ruler.
4. Take a reading on the ruler – this is the length
of the unstretched spring. Fill it in on the little table.
5. Carefully hook the base of the weight stack onto the bottom of the
spring. This weighs 1.0 newton (1.0 N).
6. Take a reading on the ruler – this is the length of the spring when a force
of 1.0 N is applied to it.
7. Add further weights. Measure the length of the spring each time. Record
your results in the table given.
8. To calculate the extension you subtract the length of the unstretched
...
spring from each of your length readings.
9. Repeat this experiment making sure to note down the new unstretched
spring length in case of any permanent deformation.
10. Keep your practical equipment out. Once you have plotted your graph
place an irregular object on the end of the spring. Record the extension.
11. Use your graph to state the force that the object has applied on the
spring.
12. Calculate the objects mass using W = mg
Hooke’s law states that: “The extension of an elastic object is directly
proportional to the force applied to it:
F=kxe
1.
F is the force in newtons, N
k is the 'spring constant' in newtons per metre, N/m
e is the extension in metres, m
This equation works as long as the elastic limit (the limit of proportionality) is
not exceeded.
Forces in a solid are bound together by strong electrostatic forces.
When they are squashed the particles are forced closer together and these
force separating them increases. When stretched these forces will also try to
return them to their original positions.
Required Practical – Hooke’s Law
Variables:
Length of unstretched spring (cm)
Test 1
Test 2
The variable we will change is (Independent Variable)…
.
The variable that we will measure is (Dependent Variable)……
The variables that I will keep the same are (Control Variable)………
Test 1
Force
added (N)
Test 2
Average
Length
Length
Extension
on
Extension
on
Extension
(cm)
ruler
(cm)
ruler
(cm)
(cm)
(cm)
Data Analysis:
Plot a scatter graph with:

‘Force added (N)’ on the x-axis

‘Extension (cm)’ on the y-axis.
0
1
2
Draw a line of best fit through your points. This should be a straight line and you will
need to use a ruler. Do NOT dot to dot.
In order to calculate the spring constant you will need to calculate the gradient of your
graph. The gradient is found by doing the following:
3
Change in Y ÷ Change in Y
4
5
6
7
What is the spring constant of
the spring? (Give your
measurement in N/cm)