| Exam Board | OCR |
|---|---|
| Module | Further Mechanics (Further Mechanics) |
| Year | 2021 |
| Session | June |
| Marks | 9 |
| Topic | Power and driving force |
| Type | Towing system: horizontal road |
| Difficulty | Standard +0.3 This is a straightforward multi-part mechanics question testing standard power-energy relationships (P=Fv, work-energy principle) with clear given values and routine calculations. Part (a) requires integrating power to find kinetic energy, parts (b) and (c) use P=Fv with force equilibrium. While it requires multiple steps and careful bookkeeping across three parts, each individual calculation follows standard textbook methods without requiring novel insight or complex problem-solving strategies. |
| Spec | 6.02k Power: rate of doing work6.02l Power and velocity: P = Fv |
1 A car of mass 800 kg is driven with its engine generating a power of 15 kW .
\begin{enumerate}[label=(\alph*)]
\item The car is first driven along a straight horizontal road and accelerates from rest.
Assuming that there is no resistance to motion, find the speed of the car after 6 seconds.
\item The car is next driven at constant speed up a straight road inclined at an angle $\theta$ to the horizontal. The resistance to motion is now modelled as being constant with magnitude 150 N .
Given that $\sin \theta = \frac { 1 } { 20 }$, find the speed of the car.
\item The car is now driven at a constant speed of $30 \mathrm {~ms} ^ { - 1 }$ along the horizontal road pulling a trailer of mass 150 kg which is attached by means of a light rigid horizontal towbar.
Assuming that the resistance to motion of the car is three times the resistance to motion of the trailer, find
\begin{itemize}
\item the resistance to motion of the car,
\item the magnitude of the tension in the towbar.
\end{itemize}
\end{enumerate}
\hfill \mbox{\textit{OCR Further Mechanics 2021 Q1 [9]}}