Question

A block of mass 1 kg slides down a rough inclined plane starting from rest. By the time it reaches point A, its potential energy decreases by 10 J and kinetic energy increases to 5J. By the time it reaches point B, its kinetic energy will be

• A. 5 J
• B. 10 J
• C. 15 J
• D. 20 J

Answer 1

The correct option is B 10 J

Decrease in potential energy - work done by friction = Increase in kinetic energy.

$\Delta K.E.=mgh-\mu mgcos\theta x$
where $x$ is the distance moved on the inclined plane and h is the height by which it went down.

By the given data we will get $\mu mgcos\theta x=5$

Applying the same equation in the next half motion, we will get the kinetic energy as 10 J.