Question

A block of mass 5 kg is sliding on a smooth floor with a velocity of $20m{s}^{-1}$. The amount of work required to stop it is:

• A. negative
• B. equal to the potential energy of the block
• C. equal to the kinetic energy of the block
• D. positive

Answer 1

Answer: (A), (C)

equal to the kinetic energy of the block

The work done to stop the block would be negative as the force applied would be opposite to the direction of motion so as to stop the moving block. Since the body possesses only kinetic energy (due to its motion) and no potential energy (as there is no mention of its position, so we assume it to be at ground level), the work required to stop the block will be equal to its kinetic energy.