A block slides down a rough ramp (with friction) of height h . Its initial speed is zero. Its final speeds at the bottom of the ramp is v . Choose the system to be the block and the Earth.

While the block is descending, its kinetic energy:

a. Increases.
b. Decreases.
c. Remains constant.

a. Increases

Explanation:

By the definition we know that the acceleration is the rate of change in velocity and here we have acceleration component in the direction of motion of the block.

Mathematically:

when the body is moving down:

where:

final velocity of the block

initial velocity of the block

acceleration due to gravity

time of observation during the instance of motion

As we know that kinetic energy is given as:

where:

mass of the block which remains constant (macroscopically)

velocity of the block (which increases here as the body descends)

c. magnitude and direction

it is a negative acceleration