Chapter 21.2, Problem 31PP

To determine

The forces acting on the oil drop, regardless of its acceleration. Also, the forces acting on the drop if it is falling at a constant velocity.

Explanation of Solution

Introduction:

The gravitational force acting on the falling body is due to the Earth’s gravity and is always acting in the downward direction. Friction force by air on any object arises when that object travels through air and is due to the collision between the air particles and the object.

There are two forces acting on the falling oil drop. One is gravitational force which is acting in the downward direction, and another one is friction force by air which is acting in the upward direction.

If the drop falls with constant velocity, then the magnitude of the two forces acting on it will be equal.