Question

A ball of mass 10 g is dropped from a certain height. At 50 m height, its KE is equal to its PE. Calculate its PE at the topmost point and TE midway.

• A. 10 J and 10 J
• B. 10 J and 20 J
• C. 20 J and 10 J
• D. 20 J and 20 J

Answer 1

The correct option is A

10 J and 10 J

KE = PE when h = $\frac{{\text{h}}_{max}}{2}$.

Thus ${\text{h}}_{max}=2h=2\times 50=100m$

$\therefore$ Ball is dropped from a height of 100 m.

${\text{PE}}_{Top}={\text{mgh}}_{max}$

$=0.01kg\times 10\times 100=10J.$

Also ${\text{TE}}_{mid-way}={\text{TE}}_{anywhere}$

$={\text{PE}}_{Top}=10J$