Question

A body is dropped from a certain height. When it loses $U$ amount of its energy it acquires a velocity ${}^{\prime }{v}^{\prime }$. The mass of the body is :

• A. $2U/v^2$
• B. $2v/U^2$
• C. $2v/U$
• D. $U^2/2v$

Answer 1

The correct option is A $2U/v^2$

We know that energy is always conserved,
So loss in energy, $U$ will be equal to energy gained to acquire velocity $v$
When a body is in motion, it will have kinetic energy
So, $U=\frac{1}{2}m{v}^2$

$\Rightarrow m=\frac{2U}{v^2}$