Complete Question:
In the "before" part of Fig. 9-60, car A (mass 1100 kg) is stopped at a traffic light when it is rear-ended by car B (mass 1400 kg). Both cars then slide with locked wheels until the frictional force from the slick road (with a low ?k of 0.15) stops them, at distances dA = 6.1 m and dB = 4.4 m. What are the speeds of (a) car A and (b) car B at the start of the sliding, just after the collision? (c) Assuming that linear momentum is conserved during the collision, find the speed of car B just before the collision.
Answer:
a) Speed of car A at the start of sliding = 4.23 m/s
b) speed of car B at the start of sliding = 3.957 m/s
c) Speed of car B before the collision = 7.28 m/s
Explanation:
NB: The figure is not provided but all the parameters needed to solve the question have been given.
Let the frictional force acting on car A,  ............(1)
............(1)
Since frictional force is a type of force, we are safe to say  .......(2)
.......(2)
Equating (1) and (2)

a) Speed of A at the start of the sliding

b) Speed of B at the start of the sliding

Let the speed of car B before collision = 
Momentum of car B before collision = 
Momentum after collision = 
Applying the law of conservation of momentum:
 
 

