Question

A small sphere of mass m is dropped from a great height. After it has fallen 100 m, it has attained its terminal velocity and continues to fall at that speed. The work done by air friction against the sphere during the first 100 m of fall is ______.

पर्याय

• greater than the work done by air friction in the second 100 m. 

• less than the work done by air friction in the second 100 m.

• equal to 100 mg.

• greater than 100 mg.

Answer 1

A small sphere of mass m is dropped from a great height. After it has fallen 100 m, it has attained its terminal velocity and continues to fall at that speed. The work done by air friction against the sphere during the first 100 m of fall is less than the work done by air friction in the second 100 m.

Explanation:

The body begins at rest and gradually increases its velocity until it reaches maximum velocity after 100 meters (terminal velocity). Furthermore, air friction, or viscous force proportional to velocity, is modest at first and increases to a maximum at v = V_T. Hence, work done against air friction in the first 100 m is less than the work done in the next 100 m.