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Free fall

In free fall without air resistance every body has the same acceleration, the acceleration of gravity. Near the Earth's surface it is 9.81 meters per second squared, directed downwards. A stone that is dropped has zero initial speed, so both the speed and the distance follow from the time alone. Air resistance makes light bodies fall more slowly than the formulas say. The formulas fit compact bodies over short drops best.

v = gt

speed after a fall from rest

s = \frac{1}{2}gt^2

distance fallen from rest

Symbols

$g$	acceleration of gravity, 9.81	m/s²
$t$	time of fall	s
$s$	distance fallen	m

Example

A stone is dropped from rest. After 2 s, without air resistance:

$s = \frac{1}{2} \cdot 9.81 \cdot 2^2 = 19.62$ m and $v = 9.81 \cdot 2 = 19.62$ m/s.

Choose downwards as the positive direction when calculating a fall, so both acceleration and speed are positive.

Practise motion for free →

← Equations of motion · Newton's second law →

Part of Physics 1: Motion.