(a)[1]
Explain what the term work done means.
(b)
A boy on a board $B$ slides down a slope, as illustrated in Fig. 3.1. The slope makes an angle of $30^\circ$ with the horizontal. The total resistive force $F$ acting on $B$ is constant.
(b(i))[1]
State a word equation that relates the work done by force $F$ on $B$ to the changes in potential and kinetic energy.
(b(ii)-1)[2]
The boy on the board $B$ travels down the slope with velocity $v$. The way $v$ changes with time $t$ is shown in Fig. 3.2. The total mass of $B$ is $75\ \text{kg}$. For $B$, from $t = 0$ to $t = 2.5\ \text{s}$, show that the distance travelled down the slope is $9.3\ \text{m}$.
(b(ii)-2)[3]
Calculate the increase in kinetic energy.
(b(ii)-3)[3]
Calculate the decrease in potential energy.
(b(ii)-4)[3]
Calculate the resistive force $F$.