Chapter 6, Problem 47A

As a sky diver falls faster and faster through the air (before reaching terminal speed), does the net force on her increase, decrease, or remain unchanged? Does her acceleration increase, decrease, or remain unchanged? Defend your answers.

To determine

Whether the net force and acceleration increases, decreases or remains unchanged.

Answer to Problem 47A

The net force as well as the acceleration on the skydiver decreases.

Explanation of Solution

Introduction:

During the fall of the skydiver, there are two forces acting on her. The force of weight is pulling her downwards and the air drag is pushing her upwards.

So, the force of weight is given by: $W=mg$

And, the air drag is $f$

So, the net force is given as: $F_{net}=mg-f$

As the skydiver falls faster and faster, the resistance of air increases but the weight factor remains constant. Due to this, the net force decreases. Now, using the Newton’s second law of motion: $F=ma$

Hence, force is directly proportional to the acceleration which results in the decreasing acceleration with decrease in net force.

Conclusion:

So, the net force as well as the acceleration on the skydiver decreases.