Question

A car has a kinetic energy of 1.9 × 103 joules. If the velocity of the car is decreased by half, what is its kinetic energy?

Answer 1

1/2 m(v/2)^2 = 1/2 m*v^2/4 = 1/4 (1/2 mv^2)
so, halving the velocity reduces the KE by a factor of 4.