3️⃣ P2 Forces - Investigate the effect of forces on springs

Question 1

There are different ways to investigate the relationship between force and extension for a spring. In this suggested practical activity, it is important to:

Answer 1

• make and record length accurately
• measure and observe the effect of force on the extension of springs
• collect the data required to plot a force-extension graph

Question 2

Aim of the experiment

Answer 2

To investigate the relationship between force and extension for a spring

Question 3

Method

Answer 3

1. Secure a clamp stand to the bench using a G-clamp or a large mass on the base.
2. Use bosses to attach two clamps to the clamp stand.
3. Attach the spring to the top clamp, and a ruler to the bottom clamp.
4. Adjust the ruler so that it is vertical, and with its zero level with the top of the spring.
5. Measure and record the unloaded length of the spring.
6. Hang a 100 g slotted mass carrier (weight 0.98 N) from the spring. Measure and record the new length of the spring.
7. Add a 100 g slotted mass to the carrier. Measure and record the new length of the spring.
8. Repeat step 7 until you have added a total of 1,000 g.

Question 4

Results

Record your results in a suitable table - what’s the column headings

Answer 4

Force (N) Length (mm) Extension (mm)

Question 5

How to calculate extension

Answer 5

extension = length - unloaded length

Question 6

Analysis - (3 steps)

Answer 6

1. For each result, calculate the extension: extension = length - unloaded length
2. Plot a line graph with extension on the vertical axis, and force on the horizontal axis. Draw a suitable line or curve of best fit.
3. Identify the range of force over which the extension of the spring is directly proportional to the weight hanging from it.

Question 7

Evaluation - how to improve accuracy of length measurements

Answer 7

It is important to keep the ruler vertical.

Suggest another way to improve the accuracy of the length measurements. - maybe check advanced info and think of one

Question 8

3 Hazards, consequences and control measures

Answer 8

.

You should take care that you do not add too many masses to the spring as this will break the spring. You should also take care when adding masses that the equipment doesn’t topple over. Eye protection must be worn.

Question 9

OCR method

Answer 9

1. Set up apparatus as shown below but do not hang the mass hanger or masses on the spring yet.
2. Measure the original length of the spring and record it in your results below.
3. Now start adding the mass hanger and masses. After each mass is added and the spring is stationary read off the new length of the spring.
4. Calculate the extension of the spring after each mass is added by using :
   Extension = new length (cm) – original spring length (cm)
5. Record results in the table below
6. Convert the mass (kg) into weight (Force, N) by using the equation:
   Weight (N) = mass (kg) x gravitational field strength (N/kg) where g = 10 N/kg
7. Keep adding masses until you have 10 results or the limit of proportionality is reached (this is the point at which the spring will no longer return to its original length when the masses are removed)
8. Repeat the above 3 times and calculate an mean value
9. Plot a graph of force (N) against extension (m)
10. Calculate the spring constant of the spring by rearranging the equation:
    force exerted by a spring (N) = extension (m) x spring constant (N/m)
11. Calculate the spring constant of the spring by calculating the gradient of your graph
12. Calculate the work done in stretching the spring by working out the area under the graph
13. Calculate the energy transferred in stretching by using the equation:
    energy transferred in stretching (J) = 0.5 x spring constant (N/m) x (extension (m))2

Question 10

Note

Answer 10

The advance info says springs + magnets.

How does one Investigate the effects of forces on the extension of springs and ‘magnets’.??

Question 11

(b) (i) Work out the spring constant of a spring if it extends by 12 cm when a mass of 0.14 kg is attached to it. [5 marks]

N/m

(b) (ii) Work out what the extension of the same spring would be if a force of 4 N was applied.
[3 marks]

M

Question 12

Why does the line for B have a different shape to the others? [2 marks]

Answer 12

2b [2 marks]
It has reached its limit of proportionality 
So no longer obeys Hooke’s law 