A body of mass $1 \mathrm{~kg}$ of thrown upwards with a velocity $20 \mathrm{~m} / \mathrm{s}$. It…
A body of mass $1 \mathrm{~kg}$ of thrown upwards with a velocity $20 \mathrm{~m} / \mathrm{s}$. It momenetarily comes to rest after attaining a height of $18 \mathrm{~m}$. How much energy is lost due to air friction ?
$\left(\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\right)$
$10 \mathrm{~J}$
$20 \mathrm{~J}$
$30 \mathrm{~J}$
$40 \mathrm{~J}$
Solution
Loss of energy $=\frac{1}{2} \mathrm{mv}^2-\mathrm{mgh}=20 \mathrm{~J}$