Question

The velocity of a body becomes half and mass becomes double. Its kinetic energy will be:

• A. Two times
• B. Half
• C. Four times
• D. None of these

Answer 1

The correct option is C

Four times

Step 1: Given data

Let

Mass of a body = $mkg$

Velocity of a body = $v\frac{m}{sec}$

New mass of a body = $2m$

New velocity of a body = $\frac{v}{2}$
Step 2: Formula used

Kinetic Energy of a body, $K.E=\frac{1}{2}m{v}^2$
Step 3: Finding kinetic energy

New kinetic energy; $$\begin{gathered} K.E_{new}=\frac{1}{2}\left(2m\right){\left(\frac{v}{2}\right)}^2 \\ K.E_{new}=\frac{1\times 2m\times v^2}{2\times 4}=\frac{1}{4}m{v}^2=\frac{1}{4}K.E \end{gathered}$$
Therefore, its kinetic energy becomes 4 times.

Hence, option (C) is correct.