If friction is the only force acting on an object during a given physical process, which of the following assumptions can be made in regard to the object’s kinetic energy? a. the kinetic energy decreases. b. the kinetic energy increases. c. the kinetic energy remains constant. d. the kinetic energy decreases and then increases.

a. The Kinetic Energy decreases.

Explanation:

The kinetic energy decreases because the force of friction opposes the motion of the object decreasing its kinetic energy converting the decrease in kinetic energy in heat ( thermal energy).

One dramatic example of this is in the case of an airplane that has aborted takeoff  by braking in an emergency. The airplane cannot takeoff again ( even if the cause of the emergency has been solved )during several hours because the brakes and tires have to cool due to the massive conversion of kinetic energy into heat .

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.

this would be about 43%