Question

A particle of mass 1 kg was sliding with a velocity of 10 m/s on a rough floor. It comes to rest after 5 s. The rate at which the floor warms up(in watts) is

• A. 10W
• B. 25
• C. 40
• D. 50

Answer 1

The correct option is A

10W

The rate at which the floor warms up is the rate at which friction does work. Due to friction between floor and particle, heat would be produced and the work done by friction would be dissipated as heat.

Frictional work, which will cause the moving body to come at rest, is equal to the initial kinetic energy of the body
Hence, frictional work $=\frac{1}{2}\times m\times v^2=0.5\times 1\times 100=50J$

So, the rate at which floor warms up would be equal to the rate of frictional work $=\frac{50}{5}=10W.$

The whole of the kinetic energy possessed by the body would be dissipated as heat due to the negative work done by friction.