Forces Notes #3

pages 96 – 104 in yer textbook

Gravity• Gravity is an attractive force that exists between

all objects that have mass.• The law of universal gravitation: The greater the

mass – the stronger the gravity, and the closer the objects, the stronger the gravity.

• Weight – gravitational force exerted on an object. Changes based on what planet yer on.

• Mass – the amount of matter that makes up an object. Never changes – unless you carve a piece off.

• What’s the diff between weight and mass?

Friction

• Friction – a force that opposes movement between two surfaces.

• Frictional force becomes smaller as the surfaces become smoother.

• Static friction – keeps objects from moving at all.

• Sliding Friction – resistance you feel when you push something.