A student wants to investigate how the terminal velocity of a streamlined capsule falling through a viscous liquid depends on its mass. They are provided with a tall glass cylinder filled with castor oil, a hollow plastic capsule, several identical steel bearings (which can be sealed inside the capsule to vary its mass), a stopwatch, and a metre rule.
Describe an investigation to show how the terminal velocity of the capsule depends on the number of steel bearings inside it.