Question

A body of mass $4 kg$ is thrown upward with a velocity of $40 m / s$ it comes to rest after attaining maximum height of $30 m$. How much energy is lost due to air friction?

• A. $2000 J$
• B. $118 J$
• C. $1800 J$
• D. $1810 J$

Answer 1

Answer: (A)

Initial energy of body $K.E =\frac{1}{2} m v^{2}=\frac{1}{2} \times 4 \times 40 \times 40$
=3200 J
At highest point, energy possesses in the form of
potential energy $P . E$ mgh $=4 \times 10 \times 30=1200 J$
Energy lost due to air friction is
$\Delta E=E_{i}-E_{f}$
$\Delta E =3200-1200$
$\Delta E =2000 J$