Question

A ball is thrown vertically up wards from the ground. Regarding the work done by air resistance, which of the following is correct?

• A. Work done is positive during the ascent and negative during the descent
• B. Work done will becomes zero.
• C. Work done is negative during the ascent and negative during the descent
• D. Work done will be same.
  

Answer 1

The correct option is C Work done is negative during the ascent and negative during the descent

Work done = $Fs=Fs$ $\cos \theta$

In air resistance , the force always act oppsoite to the direction of motion so $\theta ={180}^{\circ }$

$\cos \theta =-1$

Work done = $-Fs$

So the work done is negative during the ascent and negative during the descent