How to play Drop Test
- Choose a drop and read the height h and the value of g.
- Use h = ½·g·t² for the fall time, or v = √(2·g·h) for the impact speed.
- Type your answer and press Play. The ball falls from rest and leaves a strobe image every 0.1 s.
- Compare your answer with the landing time and speed. Pause or step to read the height and velocity on the way down.
Free fall: the same acceleration for every object
Near the Earth's surface, and without air resistance, every falling object speeds up by 9.8 m/s every second: its acceleration is g = 9.8 m/s², downward. Released from rest, its velocity is v = g·t and the distance fallen is h = ½·g·t². So the fall time from a height h is t = √(2h ÷ g), and the speed at the ground is v = √(2·g·h). Mass does not appear: a heavy ball and a light ball dropped together land together.
A focused learning model
The ball is treated as a point released from rest. g is constant over the drop and air resistance is ignored: a good model for a dense ball over a few metres, but not for a feather or a parachutist. Touchdown is solved exactly at t = √(2h ÷ g), and the velocity just before contact is kept. The drop plays in real time.