Problem 6CQ

Two expressions were used for the drag force experienced by a moving object in a liquid. One depended upon the speed, while the other was proportional to the square of the speed. In which types of motion would each of these expressions be more applicable than the other one?

Solution to 6CQ

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We need to define where the two equations of the drag forces will be applicable.

We know that when a body is moving in a fluid, there is a resistance provided by the fluid to the motion of the object. The drag force is nothing but a frictional force applied to the object during motion in a medium. A skydiver falling through the air, an aircraft maneuvering in air, a steel ball dropped in a liquid or a parachute opened in air, all of these situations give rise to drag force.

Thus, we can define drag force as a resistance offered by the medium when an object is moving through it.

Generally there are two equations for drag force.

First equation: The quadratic expression:-

…………………………….. (1)

Here,

is the drag force.

is the drag coefficient.

is the density of the medium.

is the cross- sectional area of the object

is...