4 A car collided into a lorry that was crossing a busy road. The speed
limit on the road was 60 miles per hour (27 m/s) (Figure 4).
The following measurements were made by police officers at the
scene of the crash:
The car and lorry ended up 6m from the point of impact.
The car's mass was 750 kg, and the lorry's mass was 2150 kg.
The speed of a vehicle for a braking distance of 6m is 9 m/s.
a Use this speed to calculate the momentum of the car and the
lorry immediately after the impact.
b Use conservation of momentum to calculate the velocity
[1 mark]
of the
car immediately before the collision.
[3 marks]
c Work out whether or not the car was travelling over the 60 mph
speed limit before the crash.
[1 mark]