Physics 9702 · AS & A Level · Momentum and Newton's laws of motion
Momentum and Newton's laws of motion — practice question
As shown in Fig. 3.1, a block is dragged in a straight line across a rough horizontal surface by a force X that varies.
Air resistance is negligible. Assume that the surface exerts a constant frictional force of magnitude 2.0\,\text{N} on the block.
Fig. 3.2 shows how the block’s momentum p varies with time t.
(a)[1]
State Newton’s second law of motion in terms of momentum.
(b(i))[1]
From Fig. 3.2, determine the magnitude of the resultant force acting on the block at time $t = 2.0\,\text{s}$.
(b(ii))[1]
From Fig. 3.2, determine the magnitude of force $X$ on the block at time $t = 2.0\,\text{s}$.
(c)[3]
Using Fig. 3.3, sketch a graph showing how force $X$ varies with time $t$ from $t = 0$ to $t = 6.0\,\text{s}$.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “(resultant) force is proportional to the rate at which momentum changes” …