Question

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.

Answer 1

Answer:

a. Increases

Explanation:

• Conceptually, when a block of certain mass slides on the rough ramp kept on the earth which happens under the influence of gravity.

• The block is initially at rest but as the acceleration due to gravity acts on the block at the ramp. The ramp is rough so it applies kinetic friction on the moving block as the block slides down the slope.

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:

$v=u+gt$

where:

$v=$ final velocity of the block

$u=$ initial velocity of the block

$g=$ acceleration due to gravity

$t=$ time of observation during the instance of motion

• From above it is clear that the velocity of the block will increase as the time passes during the motion.

As we know that kinetic energy is given as:

$KE=\frac{1}{2} \times m.v^2$

where:

$m=$ mass of the block which remains constant (macroscopically)

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