Question

800 g ball is pulled up a slope as shown in the figure. Calculate the potential energy it gains.

• A. 1.96 J
• B. 1.57 J
• C. 7.84 J
• D. 1.26 J

Answer 1

The correct option is B 1.57 J

$\sin \theta =\frac{20}{50}$

$\theta ={\sin }^{-1}\left(\frac{2}{5}\right)=23.58°$

Work is done against the $mg\sin \theta$ component.

$W=\overrightarrow{F}.\overrightarrow{S}=-mg\sin \theta \times 50=-800\times {10}^{-3}\times 9.8\times \sin \left(23.58°\right)\times 50\times {10}^{-2}=-0.8\times 9.8\times \frac{2}{5}\times 50\times {10}^{-2}=-1.5J$

Due to work-energy theorem ,this work done is equal to change in potential energy.

Therefore potential energy gained by the body $=1.57J$