M2 June 2015 Q1
1. A van of mass 900 kg is moving down a straight road that is inclined at an angle \(\theta\) to the horizontal, where \(\sin\theta = \dfrac{1}{30}\). The resistance to motion of the van has constant magnitude 570 N. The engine of the van is working at a constant rate of 12.5 kW.
At the instant when the van is moving down the road at 5 m s\(^{-1}\), the acceleration of the van is \(a\) m s\(^{-2}\).
Find the value of \(a\). (5)
| Scheme | Marks |
|---|---|
| \(12500 = 5F\) | B1 |
| \(F + 900g\sin\theta - 570 = 900a\) | M1 A2 |
| \(a = 2.47\ \ (2.5)\) | A1 |
| (5) |
Notes
B1 Use of \(P = Fv\)
M1 Use of \(F = ma\) parallel to the slope. All 4 terms required. Condone sign errors and sin/cos confusion. 12500 in place of F is M0 – dimensionally incorrect
A2 Correct unsimplified equation. -1 each error
Working with the positive direction up the slope is acceptable for the first 4 marks, but their final answer must be positive.