In the "before" part of Fig., 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 `mu_k` of 0.10) stops them, at distances `d_A` = 8.2 m and `d_B` = 6.1 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. (d) Explain why this assumption may be invalid.

Answer

(a)4.0 m/s ; (b) 3.5 m/s ; (c) 6.6 m/s