Question

A 930 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 2.6 m before stopping. The police officer, knowing that the coefficient of kinetic friction between tires and road is 0.80, calculates the speed of the sports car at impact.

what was the speed?

Answer 1

Vf^2=Vi^2+2ad

a= frictionforce/mass where friction force is mu*(massbothcars)g

Answer 2

let me check that. Energy wise

1/2 masssportscar*Vi^2=frictionforce*massboth cars*distance

Vi^2= 2* mu(massbothcars)distance/masssportscar

I am glad I checked it.