Physics 9702 · AS & A Level · Density and pressure
Density and pressure — practice question
A cylindrical disc with mass $0.24\,\text{kg}$ and a circular cross-sectional area $A$ is shown in Fig. 3.1. It rests on horizontal ground, as in Fig. 3.2. A force X, with magnitude $8.9\,\text{N}$, acts at an angle of $30^{\circ}$ to the horizontal. The disc moves across the ground at constant speed $0.60\,\text{m s}^{-1}$.
(a)[2]
Determine the rate at which force X does work on the disc.
(b)[3]
The force X together with the disc’s weight produces a combined pressure of $3500\,\text{Pa}$ on the ground. Calculate the cross-sectional area $A$ of the disc.
(c(i))[1]
Newton’s third law says that forces occur in pairs. One pair consists of the disc’s weight and force Y. State the direction of force Y.
(c(ii))[1]
State the name of the body on which force Y acts.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “$P = Fv$” …