Question

A small sphere starts falling from a very large height and after falling a distance of $100m$ it attains the terminal velocity and continues to fall with this velocity. The work done by the atmosphere during the first fall of $100m$ is:

• A. Greater than the work done for next fall of $100m$
• B. Less than the work done for next fall of $100m$
• C. Equal to $100mg$
• D. Greater than $100mg$

Answer 1

The correct option is B Less than the work done for next fall of $100m$

In the first $100m$ body starts from rest and its velocity goes on increasing and after $100m$ it acquire maximum velocity(terminal velocity). Further, air friction i.e. viscous force which is proportional to velocity is low in the beginning and maximum at $v=v_T$.

Hence work done against air friction in the first $100m$ is less than the work in next $100m$.