Multiple choiceQuestion 1 · Recall
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By the end you can solve problems on objects falling freely (dropped or thrown, with air resistance negligible) using the suvat equations with downwards and a sign convention you stick to.
In 1971, Apollo 15 astronaut David Scott stood on the Moon, held up a hammer and a falcon feather, and let go. They hit the dust together.
No air means no air resistance, so the only force on each is its weight. A heavier object has a bigger weight, but also more mass to get moving, and the two cancel exactly (you'll see why with in Dynamics). So every object falls with the same acceleration, whatever its mass.
Near the Earth's surface the gravitational field is very nearly uniform, so that acceleration is constant. Constant acceleration in a straight line? That's a suvat licence.
Acceleration of free fall, g
The acceleration of an object falling with no force on it except its weight (air resistance negligible). Near the Earth's surface , directed vertically downwards, and it is the same for every object.