A 930-kg sports car collides into the rear end of a 2000-kg SUV stopped at a red light. The bumpers lock, the brakes are locked, and the two cars skid forward 2.8 m before stopping. The police officer, estimating the coefficient of kinetic friction between tires and road to be 0.80, calculates the speed of the sports car at impact.

2.103 m/s

Explanation:

Given

mass of sports car

mass of SUV

Suppose u is the velocity if sports car before collision

Conserving momentum we get

After collision the combined mass drag 2.8 m and finally stops

From work energy theorem work done by friction is equal to change in kinetic energy of the  combined mass system

where

Initial velocity