Question

A 300 g mass has a velocity of $(3\hat{i}+4\hat{j})m/s$ at a certain instant. What is its kinetic energy?

• A. 1.35 J
• B. 2.4 J
• C. 3.75 J
• D. 7.35 J

Answer 1

The correct option is C

3.75 J

$\overrightarrow{v}=(3\hat{i}+4\hat{j})\therefore speed=v=\sqrt{3^2+4^2}=5m/s$. So kinetic energy = $\frac{1}{2}m{v}^2=\frac{1}{2}\times 0.3\times (5{)}^2=3.75J$