Weight and Mass

Mass A measure of how much stuff an object contains. SI unit is kg

Weight This is the force due to gravity It is the gravitational force between two objects, e.g. you and the Earth.

Mass stays the same where ever you go, but weight depends on the gravitational field you are in.

On Earth, weight is mass x g g = 10 N/kg W = mg

On the moon, weight is mass x g g = 1.6 N/kg W = mg

Calculate: The weight of a 60 kg person on the Moon and on the Earth The mass of some one with a weight of 549N (on Earth)

g Gravity acts on all objects with mass g can also be written as 10 m/s2 since any object will fall with an acceleration of 10 m/s2 This is called freefall. The mass of an object does not affect how it falls. Any two objects when dropped from the same height will hit the floor at the same time.

ASSUMING NO AIR RESISTANCE

The only reason we think heavy object fall faster is because in our experience that seems to be the case but we always have air resistance. Air resistance means the lighter objects reach terminal velocity earlier and therefore travel slower. Galileo realised this in the 1600’s. But had no way to prove it. It wasn't proved until…

https://www.youtube.com/watch?v=03SPBXALJZI https://www.youtube.com/watch?v=E43-CfukEgs