Question

A block is freely starts sliding down on a rough inclined plane from a vertical height $5m$. The block reaches the bottom of inclined plane then it just describes vertical circle of radius $1.2m$ along smooth track. The percentage of energy wasted due to friction is:

• A. $20$ %
• B. $30$ %
• C. $40$ %
• D. $60$ %

Answer 1

Answer: (C)

$40$ %

Minimum height from which the body has to be dropped on a plane to just complete the vertical circular motion is $\frac{5r}{2}=\frac{5\times 1.2}{2}=3m$
So, a minimum height of $3m$ is enough for the body to complete circular motion of radius $1.2m$.
But here the body is released from a height of $5m$, still is just completes the loop, implies that the loss in energy is because of the friction.
The percentage energy wasted due to friction$=\frac{h-h_{min}}{h}\times 100=\frac{5-3}{5}\times 100=40$%