Question

A ball is thrown vertically upwards. Determine the work done by gravity when the ball travels upto a height of $15\text{m}$. Mass of the ball $=1\text{kg}$. Acceleration due to gravity $\left(g\right)$ $=10{\text{m/s}}^2$.

• A. $150\text{J}$
• B. $100\text{J}$
• C. $-150\text{J}$
• D. Zero

Answer 1

The correct option is C $-150\text{J}$

We know that work done by gravity $\left(W_g\right)$ is given by
$W_g=\overrightarrow{F}.\overrightarrow{S}$, here force due to gravity is its weight $mg$ and displacement is given as, $S=15\text{m}$

Hence workdone will be

$W_g=mgscos{180}^{\circ }=-1\times 10\times 15$
$Wg=-150J$

Hence option C is the correct answer