Question

A 980-kg sports car collides into the rear end of a 2500-kg SUV stopped at a red light. The bumpers lock, the brakes are locked, and the two cars skid forward 2.7m 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.

What was the speed sports car at impact?

Answer 1

Step-by-step explanation:

The work of friction will be Fn * .8 x d

Fn = ( m1 + m2) g = ( 980+2500 kg) (9.81) = 34139 N

Work f friction = Ffriction x d

= 34139 N * .8 x 2.7 m = 73740 J

this equals the sports car's KE

73740 J = 1/2 mv^2

73740 = 1/2 ( 980)(v^2 ) v = 12.3 m/s