This model was built to explore the drag force that acts on a moving sphere in a fluid. It reproduces the expected velocity-time graph of a skydiver quite well.
The equation used includes two coefficients, one which controls the “viscous” term and controls the dependence on the radius and velocity of the sphere, and a second which controls the “pressure” term which depends on the area of the sphere and the velocity squared.
Two models are provided, one which allows the user to specify the first and second terminal speeds (those reached before and after pulling the parachute respectively) and one which allows for free choice of all parameters.
It might be useful to lock the vertical axis scale so that changes in the terminal speeds can be explored in a more visual way.
This resource could be used by A-Level students in a discussion about terminal speed or about how to build simple models in excel. This skill can be applied to the discharging and charging of capacitors, and radioactive decay, to produce the expected exponential relationships without requiring calculus.