Question

A 5 kg ball when falls through a height of 20 m acquires a speed of 10 m/s. Find the work done by air resistance​

Answer 1

Answer:

speed gained in absence of air is given by

v^2 - 0^2 = 2×10 ×20

v^2 = 400m/s

speed gained in presence of air is given by

v^2= 10^2=100

so work done by air

1/2 × 5 × (100-400) = -150×5= - 750 joule

clearly the air resistance tries to decrease the speed of ball hence work done by it must be negative.

Answer 2

Hi

W= - 750 J

Hope you understood

Thank you!!