Acceleration of free fall - Higher
The acceleration of a falling object can be calculated using Newton鈥檚 Second Law, F = ma
If a skydiver has a massThe amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g). of 60 kg. Her weightThe force acting on an object due to the pull of gravity from a massive object like a planet. The force acts towards the centre of the planet and is measured in newtons (N). is found using:
W = mg
W = 60 kg x 10 N/kg
W = 600 N
If air resistance is ignored, the pull of gravity, 600 N, is the only force acting on the skydiver. Her acceleration is found using:
a = \(\frac{\text{F}}{\text{m}}\)
F = 600 N
m = 60 kg
a = \(\frac{\text{600 N}}{\text{60 kg}}\)
a = 10 m/s2.
Key points
- In the absence of air resistanceA force of friction produced when an object moves through the air. all objects fall at the same rate regardless of their mass. Near the Earth the rate is the acceleration of free fall, 10 m/s2.
- Due to the Earth鈥檚 gravity, the speed of an object dropped from a height will increase at a rate of 10 m/s every second as it falls.
- If there was no air resistance or drag, a feather and a hammer would fall at the same rate of 10 m/s2. Dropped from the same height, they would both hit the ground at the same time and travelling at the same speed.
- An object fired vertically upwards slows down at a rate of 10 m/s2. It experiences a retardation of 10 m/s2.