Force and Extension (Hooke’s Law)
Aim:
To investigate the relationship between the force applied to a spring and its extension —
and to check if it obeys Hooke’s Law.
Method:
1. Set up a clamp stand with a ruler and a spring attached securely (zero line of ruler
must be level with the bottom of the spring).
2. Hang a slotted mass hanger (with known masses) from the spring.
3. Measure and record the initial length of the spring with no masses.
4. Add one mass at a time (e.g. 100g = 1N), allow the spring to stop moving, and
measure the new length of the spring.
5. Repeat step 4 for at least 6 different masses.
6. Calculate the extension each time:
Extension = new length – original length
7. Plot a graph of Force (N) on the y-axis against Extension (cm or m) on the x-axis.
Variables:
INDEPENDENT VARIABLE: The force applied (weight = mass × gravity).
DEPENDENT VARIABLE: The extension of the spring.
CONTROL VARIABLES: Same spring, same ruler, measuring from the same point, keep the
setup stable (no swinging!).
Common Mistakes:
1. Not lining the ruler up with the spring properly – leads to dodgy measurements.
2. Measuring length instead of extension – remember to subtract original length.
3. Spring swinging or bouncing – wait for it to settle!
Risks:
1. Masses could fall – make sure clamp stand is stable and don’t overload the spring.
2. Spring could snap if overstretched – never go beyond the elastic limit.
3. Sharp ends of broken springs – be careful handling old or damaged springs.
, Investigating Acceleration
Aim:
To investigate how acceleration is affected by the force applied to an object and the mass of
the object, using a light gate, trolley, and datalogger.
Method:
1. Set up a ramp with a trolley connected to a pulley system. A string runs over the
pulley, connecting the trolley to a hanging mass (provides the force).
2. Attach a card to the top of the trolley, with a gap in the middle, so it interrupts
the light gate beam twice — this allows the datalogger to calculate the
trolley’s acceleration.
3. Place a light gate connected to a datalogger or computer at the end of the ramp to
measure the acceleration of the trolley as it passes through.
4. For investigating the effect of force:
o Keep the total mass of the system constant (trolley + hanging mass).
o Transfer masses from the trolley to the hanging hook to increase
the force (weight = mass × gravity).
5. For investigating the effect of mass:
o Keep the force (hanging mass) constant.
o Increase the mass of the trolley by adding masses to it.
6. Repeat each test 3 times and take an average to reduce error.
Variables:
INDEPENDENT VARIABLE: The mass of the hook or the trolley.
DEPENDENT VARIABLE: The acceleration of the trolley.
CONTROL VARIABLES: Same ramp angle, same trolley, same distance travelled, same light
gate position, same software.
Common Mistakes:
1. Not accounting for friction – can reduce acceleration and mess up results.
2. Letting the string go slack – string must stay taut at the start.
3. Not keeping total mass constant when changing the force – that invalidates your fair
test
Risks:
1. Trolley falling off the ramp – make sure the track is flat and secure.
2. Hanging mass dropping too quickly – stay clear and handle gently.
3. Tripping over wires or string – keep setup tidy and stable.
Aim:
To investigate the relationship between the force applied to a spring and its extension —
and to check if it obeys Hooke’s Law.
Method:
1. Set up a clamp stand with a ruler and a spring attached securely (zero line of ruler
must be level with the bottom of the spring).
2. Hang a slotted mass hanger (with known masses) from the spring.
3. Measure and record the initial length of the spring with no masses.
4. Add one mass at a time (e.g. 100g = 1N), allow the spring to stop moving, and
measure the new length of the spring.
5. Repeat step 4 for at least 6 different masses.
6. Calculate the extension each time:
Extension = new length – original length
7. Plot a graph of Force (N) on the y-axis against Extension (cm or m) on the x-axis.
Variables:
INDEPENDENT VARIABLE: The force applied (weight = mass × gravity).
DEPENDENT VARIABLE: The extension of the spring.
CONTROL VARIABLES: Same spring, same ruler, measuring from the same point, keep the
setup stable (no swinging!).
Common Mistakes:
1. Not lining the ruler up with the spring properly – leads to dodgy measurements.
2. Measuring length instead of extension – remember to subtract original length.
3. Spring swinging or bouncing – wait for it to settle!
Risks:
1. Masses could fall – make sure clamp stand is stable and don’t overload the spring.
2. Spring could snap if overstretched – never go beyond the elastic limit.
3. Sharp ends of broken springs – be careful handling old or damaged springs.
, Investigating Acceleration
Aim:
To investigate how acceleration is affected by the force applied to an object and the mass of
the object, using a light gate, trolley, and datalogger.
Method:
1. Set up a ramp with a trolley connected to a pulley system. A string runs over the
pulley, connecting the trolley to a hanging mass (provides the force).
2. Attach a card to the top of the trolley, with a gap in the middle, so it interrupts
the light gate beam twice — this allows the datalogger to calculate the
trolley’s acceleration.
3. Place a light gate connected to a datalogger or computer at the end of the ramp to
measure the acceleration of the trolley as it passes through.
4. For investigating the effect of force:
o Keep the total mass of the system constant (trolley + hanging mass).
o Transfer masses from the trolley to the hanging hook to increase
the force (weight = mass × gravity).
5. For investigating the effect of mass:
o Keep the force (hanging mass) constant.
o Increase the mass of the trolley by adding masses to it.
6. Repeat each test 3 times and take an average to reduce error.
Variables:
INDEPENDENT VARIABLE: The mass of the hook or the trolley.
DEPENDENT VARIABLE: The acceleration of the trolley.
CONTROL VARIABLES: Same ramp angle, same trolley, same distance travelled, same light
gate position, same software.
Common Mistakes:
1. Not accounting for friction – can reduce acceleration and mess up results.
2. Letting the string go slack – string must stay taut at the start.
3. Not keeping total mass constant when changing the force – that invalidates your fair
test
Risks:
1. Trolley falling off the ramp – make sure the track is flat and secure.
2. Hanging mass dropping too quickly – stay clear and handle gently.
3. Tripping over wires or string – keep setup tidy and stable.
