Question

An object of mass $m$ is moving with a constant velocity $\text{'}v\text{'}$. The work done on the object to bring it to rest is:

• A. $m{v}^2$
• B. $\frac{1}{2}m{v}^2$
• C. $mv$
• D. $\frac{1}{2}{m}^{2}v$

Answer 1

The correct option is B

$\frac{1}{2}m{v}^2$

1. An object with mass '$m$‘ moving with velocity ’$v$' has kinetic energy of $\frac{1}{2}m{v}^2$
2. In order to bring it to rest, its velocity has to be reduced to zero, and in order to accomplish that, the kinetic energy has to be drained off and sent somewhere else.
3. An external force has to absorb energy from the object, i.e. do negative work on it, equal to its kinetic energy,or $-\frac{1}{2}m{v}^2$.

Hence, the correct answer is option (B) i.e. $\frac{1}{2}m{v}^2$