M1 June 2014 Q2
2.

A rough plane is inclined at 40\(^\circ\) to the horizontal. Two points \(A\) and \(B\) are 3 metres apart and lie on a line of greatest slope of the inclined plane, with \(A\) above \(B\), as shown in Figure 2. A particle \(P\) of mass \(m\) kg is held at rest on the plane at \(A\). The coefficient of friction between \(P\) and the plane is \(\dfrac{1}{2}\). The particle is released.
| Scheme | Marks |
|---|---|
| \(R = mg\cos 40\) | B1 |
| Use of \(F = \mu R\) | B1 |
| \(mg\sin 40 - F = \pm ma\) | M1A1 |
| \(acc = 2.55\) (m s\(^{-2}\)) or 2.5 (m s\(^{-2}\)) | A1 |
| (5) |
Notes
(Deduct only 1 mark in whole question for not giving an answer to either 2 sf or 3 sf, following use of g = 9.8)
First B1 for \(R = mg\cos 40^\circ\)
Second B1 for \(F = \mu R\) seen or implied(can be on diagram)
M1 for resolving parallel to plane, correct no. of terms, \(mg\) resolved (\(F\) does not need to be substituted)
First A1 for a correct equation
Second A1 for 2.5 (ms\(^{-2}\)) or 2.55 (ms\(^{-2}\)) Must be positive.
S.C. If \(m\) is given a specific numerical value, can score max B1B1M1A0A0
| Scheme | Marks |
|---|---|
| \(v^2 = u^2 + 2as = 2 \times a \times 3\) Speed at \(B\) is 3.9 (m s\(^{-1}\)) or 3.91(m s\(^{-1}\)) | M1A1 |
| (2) | |
| (7 marks) |
Notes
M1 is for a complete method for finding speed (usually \(v^2 = u^2 + 2as\))
A1 for 3.9 (ms\(^{-1}\)) or 3.91(ms\(^{-1}\))