June 2025 Paper 1 Q5
5 A uniform rectangular lamina ABCD has a mass of 0.12 kg. Length AB is 11 cm and length AD is 20 cm.
The lamina ABCD is held by a smooth hinge at A.
A horizontal force of magnitude \(P\) N is applied at B so that the lamina is in equilibrium in a vertical plane with AD horizontal as shown in the diagram.
Show that \(P\) is 1.07 to 3 significant figures. [3]
| Scheme | Marks | AO |
|---|---|---|
| Moments about A \(0.1\times 0.12g = 0.11P\) | M1 A1 | 3.1a 2.1 |
| \(P = 1.07\) | A1 | 2.1 |
| [3] |
Notes
M1: Attempt to calculate a moment of at least one force about any point. Do not award for oblique distance(s) used without resolving the forces
A1: Correct moment of weight about A
A1: AG 1.07 obtained from correct total moment equation seen. 1.06909…
Award if full equation or \(10\times 0.12g\) and \(\frac{11.76}{11} = 1.07\) seen
Allow full credit for taking moments about another point where the correct force(s) at the hinge is seen.