A horizontal force of 100 N is applied to move a 50-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of the cart?

The net force on the cart is 100 N in the direction of its motion, so by Newton's second law we can find the acceleration a applied to it:

100 N = (50 kg) a

a = (100 N) / (50 kg)

a = 2 m/s²

The cart starts at rest and travels a distance of 10 m, so that its final velocity v satisfies

v ² - 0² = 2 (2 m/s²) (10 m)

v ²= 40 m²/s²

and so the cart ends up with kinetic energy

KE = 1/2 m v ² = 1/2 (50 kg) (40 m²/s²) = 1000 J