7.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{278c8424-38aa-48c2-bc82-af4be9234f71-11_216_1335_207_306}
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\caption{Figure 4}
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A truck of mass 1750 kg is towing a car of mass 750 kg along a straight horizontal road. The two vehicles are joined by a light towbar which is inclined at an angle \(\theta\) to the road, as shown in Figure 4. The vehicles are travelling at \(20 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) as they enter a zone where the speed limit is \(14 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). The truck's brakes are applied to give a constant braking force on the truck. The distance travelled between the instant when the brakes are applied and the instant when the speed of each vehicle is \(14 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) is 100 m .
- Find the deceleration of the truck and the car.
The constant braking force on the truck has magnitude \(R\) newtons. The truck and the car also experience constant resistances to motion of 500 N and 300 N respectively. Given that \(\cos \theta = 0.9\), find
- the force in the towbar,
- the value of \(R\).