Paper 4 Forces Drills

Q1 Force-extension experiment

A student investigates a spring by hanging different masses from it. The force $F$ and extension $x$ are recorded.

$x/\mathrm{m}$	0.000	0.010	0.020	0.030	0.040	0.050	0.065
$F/\mathrm{N}$	0.00	0.60	1.20	1.80	2.40	3.00	3.40

1. Describe how the extension should be measured accurately. [2]
2. Explain why the force may be calculated as $F=mg$ after each load has come to rest. [2]
3. Plot $F$ against $x$ on the grid below and draw an appropriate best-fit trend. [5]

4. Use the initial straight-line region to determine the force constant $k$. [3]
5. Estimate the extension at the limit of proportionality. [2]
6. State two precautions to avoid damaging the spring or invalidating the investigation. [2]

Q2 Upthrust measurement

A solid object is hung from a newton meter. Its weight in air is $3.20\mathrm{N}$. When fully immersed in water without touching the beaker, the newton-meter reading is $2.45\mathrm{N}$.

1. Calculate the upthrust on the object. [2]
2. Explain why the object must not touch the beaker. [2]
3. The density of water is $1000\mathrm{kg}{\mathrm{m}}^{-3}$. Calculate the volume of the object. [3]
4. State one method for reducing uncertainty in the immersed reading. [1]