A student investigates the balancing of a metre rule. The experimental setup has a metre rule balanced on a pivot at the 50.0 cm50.0\text{ cm}50.0 cm mark.
The student places object P with its centre at the 15.0 cm15.0\text{ cm}15.0 cm mark. Because object P covers the scale under it, explain briefly how to place this object as accurately as possible so that its centre is exactly at the 15.0 cm15.0\text{ cm}15.0 cm mark.
The distance aaa is the distance between the centre of object P and the pivot. The student places object Q on the other side of the pivot and adjusts its position to balance the rule. The centre of Q is at the 74.5 cm74.5\text{ cm}74.5 cm mark. Determine and state the distance bbb between the centre of object Q and the pivot.
The experiment is repeated for different positions of object P. The results are shown in Table 1.1:
| a/cma / \text{cm}a/cm | b/cmb / \text{cm}b/cm |
|---|---|
| 35.0 | 24.5 |
| 30.0 | 21.1 |
| 25.0 | 17.6 |
| 20.0 | 14.0 |
| 15.0 | 10.6 |
Using the first and last data points in Table 1.1, calculate the gradient GGG of the line of best fit, where aaa is on the yyy-axis and bbb is on the xxx-axis.
The gradient GGG of the graph is equal to the ratio RRR of the masses of P and Q (where R=mPmQR = \frac{m_P}{m_Q}R=mQmP). Record the ratio RRR of the masses. Give your answer to a suitable number of significant figures.
245 exam-style questions on CIE IGCSE Physics 1.5 Forces, covering 1.5.1a Forces, resultant force and motion, 1.5.1b Load–extension graphs and the spring constant, 1.5.1c Friction and drag, 1.5.1d Force, mass and acceleration, 1.5.1e Motion in a circular path, 1.5.2a Moment of a force, 1.5.2b Principle of moments and equilibrium, and 1.5.3 Centre of gravity and stability. Each one has a worked solution and a mark scheme showing where the marks go.