Question

If $E$ represents total mechanical energy of a system while $U$ represents the potential energy, then $E-U$ is:

• A. always zero
• B. always less than zero
• C. always greater than or equal to zero
• D. either positive or negative

Answer 1

Answer: (C)

always greater than or equal to zero

$E=U+K$
$E-U=K=\frac{1}{2}m{v}^2$

As $K$ is always non negative or zero, in case it is at rest.

Hence $E-U$ is always greater than or equal to zero.