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Gravity and Weight - read text page233
Gravity is a force of attraction that exists between any two objects.
- It is the weakest of the known natural forces, only becoming obvious when massive objects like stars and planets are involved.
- (e.g.Magnetic attraction is 1 X 10 40 times stronger than gravitational attraction.)
- Weight on earth is the gravitational force between an object and the Earth.
- Weight = mg where m = mass in kg, and
- g = gravitational acceleration = 9.8 m/s 2 or about 10m/s 2
- Units – Newtons (N) e .g.
mass |
Weight |
20 kg |
196 N or approx 200 N |
200 g |
1.96 N or approx. 2 N |
5 kg or approx 4.9 kg |
49 N |
- Weight decreases with increase in altitude.
- Weight increases towards the poles from the Equator since the earth is not perfectly symmetrical – (flatter at the poles thus an object at the North or South pole is closer to the centre of the Earth - Weight closer to the poles.)
Mass
- a measure of the amount of matter in an object.
- Units - kilograms (kg). Not to be confused with weight, which is a force.
Complete Motion Booklet page 7 (Question1,2)
Complete text questions page 234-235
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