Question

A $4kg$ body is thrown vertically upward from the ground with a velocity of $5m{s}^{-1}$. Its kinetic energy just before hitting the ground is

• A. $25J$
• B. $50J$
• C. $75J$
• D. $100J$

Answer 1

The correct option is B

$50J$

Step 1: Given data

Mass of body is $m=4kg$

Velocity of the body is $v=5m{s}^{-1}$

Step 2: Finding the kinetic energy of the body:

Assuming air resistance to be absent, the kinetic energy$\left(E_k\right)$ just before hitting the ground should be the same as the kinetic energy of throw.

We know that,

$$\begin{gathered} Kineticenergy\left(E_k\right)=\frac{1}{2}m{v}^2 \\ {E}_k=\frac{1}{2}\times 4\times {\left(5\right)}^2 \\ {E}_k=50J \end{gathered}$$

Thus, the kinetic energy of the body is $50J$

Hence, option (b) is correct.