Physics 0625 · IGCSE · Forces

Forces — practice question

A student carries out an investigation into how a metre ruler balances. Fig. 1.1 displays the apparatus. The metre ruler has markings from 0 to 100. It rests on a pivot at the 50.0 cm mark. Object Q has its centre positioned on the metre ruler at the 90.0 cm mark. Labels shown: load, object Q, metre ruler, pivot, bench, 50.0 cm mark, 90.0 cm mark, x, y.
(a)[2]

Determine the distance y between the 50.0 cm mark and the centre of the object Q.

(b(i))[2]

Calculate the weight W of object Q, using the equation $W = \frac{x}{y} \times 2.0\,\text{N}$. Give your answer to a suitable number of significant figures for this experiment.

(b(ii))[1]

Calculate a revised value for the weight W of object Q, using the equation $W = \frac{x}{y} \times 3.0\,\text{N}$. Give your answer to a suitable number of significant figures for this experiment.

(c)[2]

State and explain whether your two values of W are equal within the limits of experimental accuracy. Use the values of W in your answer.

(d)[1]

Explain how you ensure that the centre of object Q is directly over the 90.0 cm mark of the metre ruler. You may draw a diagram.

(e)[1]

It is difficult to find the position of the load to obtain the exact balance of the metre ruler. Explain how you try to overcome this difficulty.

(f)[2]

Determine the distance d from the 50.0 cm mark on the metre ruler to the centre of mass. Show your working.

Worked solution & mark scheme

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