Question

If a body of mass$200g$falls from a height of $200m$ and its total P.E. is converted into K.E. at the point of contact of the body with the earth's surface, then what is the decrease in P.E. of the body at the contact $(g=10m/s^2)$.

• A. $200J$
• B. $400J$
• C. $600J$
• D. $900J$

Answer 1

The correct option is B

$400J$

Step 1: Given data:

The body of mass $m=200g$

The height $h=200m$

The acceleration due to gravity $g=10m/s^2$

Step 2: Formula used:

Initial potential energy $P.E.=m\times g\times h$

Therefore,

$$\begin{gathered} P.E.=0.200kg\times 10m/s^2\times 200m \\ P.E.=400J \end{gathered}$$

Therefore, the decrease in P.E. of the body at the contact $400J$.

Hence, the correct option is (B).