A cart is initially moving at 0.5 m/s along a track. The cart comes to rest after traveling 1 m. The experiment is repeated on the same track, but now the cart is initially moving at 1 m/s. How far does the cart travel before coming to rest?
A. 1 m B. 2 m C. 3 m D. 4 m E. 8 m

D. 4 m

Explanation:

According to the work-energy theorem, the work done by the force acting on a body modifies its kinetic energy.

The car comes to rest after a given distance, so . Recall the definition of work , here F is the constant force acting on the car, d is its traveled distance and is the angle between the force and the displacement, since friction force acts opposite to the direction of motion :

We have:

Thus:

f is prop to m1xm2 double m1 double force