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. ball ↑ h moving air air blower 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 4πr³gh = PK 3 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.