Physics 9702 · AS & A Level · Momentum and Newton's laws of motion

Momentum and Newton's laws of motion — practice question

A motor pulls a log with mass $452\,\text{kg}$ up a slope using a cable, as illustrated in Fig. 2.1. The slope makes an angle of $14.0^\circ$ to the horizontal.
(a)[1]

Show that the component of the log’s weight down the slope is $1070\,\text{N}$.

(b)

The log begins at rest. A constant frictional force of $525\,\text{N}$ acts on it. It accelerates up the slope at $0.130\,\text{m s}^{-2}$.

(b(i))[3]

Calculate the cable tension.

(b(ii).1)[2]

The log starts from rest at point $S$. It is hauled a distance of $10.0\,\text{m}$ to point $P$. Calculate, for the log, how long it takes to travel from $S$ to $P$.

(b(ii).2)[1]

Calculate, for the log, the magnitude of its velocity at $P$.

(c)[4]

When the cable breaks as the log arrives at point $P$, sketch on Fig. 2.2 how the velocity $v$ varies with time $t$ for the log. The graph is to show $v$ from the start at $S$ until the log gets back to $S$.

(ii.1)[2]

Calculate, for the log, how long it takes to move from S to P.

(ii.2)[1]

Calculate, for the log, the magnitude of the velocity at P.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: Weight is $452 \times 9.81$

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