Moderate -0.3 This is a straightforward M2 work-energy-power question requiring standard application of P=Fv and F=ma with resistance forces. Part (a) uses Power = Driving Force × velocity to find force, then Newton's second law. Part (b) applies the same formula with an additional component for gravitational resistance on the incline. Both parts are routine calculations with no problem-solving insight required, making it slightly easier than average.
A lorry of mass 1500 kg moves along a straight horizontal road. The resistance to the motion of the lorry has magnitude 750 N and the lorry's engine is working at a rate of 36 kW .
Find the acceleration of the lorry when its speed is \(20 \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
The lorry comes to a hill inclined at an angle \(\alpha\) to the horizontal, where \(\sin \alpha = \frac { 1 } { 10 }\). The magnitude of the resistance to motion from non-gravitational forces remains 750 N .
The lorry moves up the hill at a constant speed of \(20 \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
Find the rate at which the lorry's engine is now working.
(3)
\begin{enumerate}
\item A lorry of mass 1500 kg moves along a straight horizontal road. The resistance to the motion of the lorry has magnitude 750 N and the lorry's engine is working at a rate of 36 kW .\\
(a) Find the acceleration of the lorry when its speed is $20 \mathrm {~m} \mathrm {~s} ^ { - 1 }$.
\end{enumerate}
The lorry comes to a hill inclined at an angle $\alpha$ to the horizontal, where $\sin \alpha = \frac { 1 } { 10 }$. The magnitude of the resistance to motion from non-gravitational forces remains 750 N .
The lorry moves up the hill at a constant speed of $20 \mathrm {~m} \mathrm {~s} ^ { - 1 }$.\\
(b) Find the rate at which the lorry's engine is now working.\\
(3)\\
\hfill \mbox{\textit{Edexcel M2 2004 Q1 [7]}}