M5 June 2014 (R) Q1
1. [In this question, \(\mathbf{i}\) and \(\mathbf{j}\) are perpendicular unit vectors in a horizontal plane.]
A bead \(P\) of mass 0.2 kg is threaded on a smooth straight horizontal wire. The bead is at rest at the point \(A\) with position vector \((4\mathbf{i} - \mathbf{j})\) m. A force \((0.2\mathbf{i} + 0.3\mathbf{j})\) N acts on \(P\) and moves it to the point \(B\) with position vector \((13\mathbf{i} + 5\mathbf{j})\) m.
Find the speed of \(P\) at \(B\). (5)
| Scheme | Marks |
|---|---|
| \(\overrightarrow{AB} = (9\mathbf{i} + 6\mathbf{j})\) | B1 |
| \((0.2\mathbf{i} + 0.3\mathbf{j}) \cdot (9\mathbf{i} + 6\mathbf{j}) = \tfrac{1}{2} \times 0.2 \times v^2\) | M1 A1 A1 |
| \(6 = v\) | A1 |
| (5 marks) |