Motion Calculator
Uniform Motion Calculator
Uniform motion is movement at a constant speed in a straight line. Use time and distance t...
Read MoreAcceleration Calculator
Acceleration is the change in velocity per unit time. Enter initial velocity, final veloci...
Read MoreFree Fall Calculator
Free fall is motion under gravity alone. Enter the drop height to get the fall time and im...
Read MoreAbout This Category
Motion questions reduce to three quantities: distance, speed and time, plus acceleration when speed changes. The pages separate constant-speed problems from accelerating ones, because mixing the two is the usual source of wrong answers.
Free fall is the accelerating case with a known acceleration, 9.81 m/s² downward. The calculator ignores air resistance, which is a good approximation for dense, compact objects over short distances and a poor one for feathers and parachutes.
Frequently Asked Questions
Can I use the average speed for an accelerating object?
Only if the acceleration is constant. Average speed is then the mean of start and end speed; with changing acceleration the distance must be integrated.
Why does free fall give a different time than a car at the same speed?
Because speed is not constant. An object falling 20 m reaches about 19.8 m/s, but at an average of 9.9 m/s — not 19.8 m/s for the whole drop.
Is 9.81 m/s² the right value everywhere?
It is the standard value at sea level at 45° latitude. It falls by about 0.3 % at the equator and rises at the poles; for schoolwork the difference is negligible.
Calculators in This Category
Sources & last update
2026-10-19