Question

A body of mass 10 kg dropped from a height 20 m, acquires a velocity of 10 m/s after falling through a distance of 20 m. What is the work done by the air resistance on the body?

• A. 750 J
• B. 1000 J
• C. 1500 J
• D. 2000 J

Answer 1

The correct option is C 1500 J

Formula,

$k=\frac{1}{2}m{v}^2$

work done by air resistance,

$=k_2-k_1$

$=\frac{1}{2}m{v}_2^2-\frac{1}{2}m{v}_1^2$

$=\frac{1}{2}\times 10\times (2\times 10\times 20)-\frac{1}{2}\times 10\times (10\times 10)$

$=2000-500=1500J$