Physics 9702/51 — October/November 2019

When a light plastic ball is placed in a vertical column of moving air, the ball becomes stationary at a height $h$, as shown in Fig. 1.1.

A student is using an air blower to create the vertical column of moving air. The student connects the motor of the air blower to a d.c. power supply.

It is suggested that the relationship between the radius $r$ of the ball and $h$ is

where $g$ is the acceleration of free fall, $P$ is the power of the motor and $K$ is a constant.

Design a laboratory experiment to test the relationship between $r$ and $h$.
Explain how your results could be used to determine a value for $K$.

You should draw a diagram, on page 3, showing the arrangement of your equipment. In your account you should pay particular attention to:

• the procedure to be followed
• the measurements to be taken
• the control of variables
• the analysis of the data
• any safety precautions to be taken.