Question

A $150gm$ mass has a velocity $2\hat{i}+6\hat{j}m/s$ at a certain instant. Its kinetic energy is:

• A. $6J$
• B. $2J$
• C. $3J$
• D. $8J$

Answer 1

The correct option is C $3J$

$\mid \overrightarrow{v}\mid =\sqrt{2^2+6^2}$ $=\sqrt{40}m/s$

$K.E=\frac{1}{2}m\mid \overrightarrow{v}{\mid }^2$

$=\frac{1}{2}\times 150\times {10}^{-3}\times 40$

$=3J$