Question

What will be the final velocity of a 5.0 g bullet starting from rest, if a net force of 45 N is

applied over a distance of 0.80 m?

Answer 1

The net force performs a total amount of work equal to

(45 N) (0.80 m) = 36 J

on the bullet, and this is in turn is equal to the change in the bullet's kinetic energy by the work-energy theorem. So we have

W = ∆K = 1/2 mv²

since the bullet starts at rest, where m = its mass and v = its final velocity.

Solve for v :

36 J = 1/2 (0.0050 kg) v² ⇒ v = 120 m/s