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
