7.
\begin{figure}[h]
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\caption{Figure 4}
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\end{figure}
Figure 4 shows a lorry of mass 1600 kg towing a car of mass 900 kg along a straight horizontal road. The two vehicles are joined by a light towbar which is at an angle of \(15 ^ { \circ }\) to the road. The lorry and the car experience constant resistances to motion of magnitude 600 N and 300 N respectively. The lorry's engine produces a constant horizontal force on the lorry of magnitude 1500 N. Find
- the acceleration of the lorry and the car,
- the tension in the towbar.
When the speed of the vehicles is \(6 \mathrm {~m} \mathrm {~s} ^ { - 1 }\), the towbar breaks. Assuming that the resistance to the motion of the car remains of constant magnitude 300 N ,
- find the distance moved by the car from the moment the towbar breaks to the moment when the car comes to rest.
- State whether, when the towbar breaks, the normal reaction of the road on the car is increased, decreased or remains constant. Give a reason for your answer.