Gravity and Friction

Gravity is...

A force of attraction between objects due to their masses.

• Gravity exists between objects even when they are not touching.

• Gravity is a non-contact force.

• It is an attractive force because it always pulls objects toward each other.

​Do you think this dog has ever studied gravity? He sure seems to know that the ball is going to fall - and where it is going to land!

• The amount of matter in an object.

• Constant, will not change.

• Common units of measurement: gram, kilogram, pound

Weight

• The measure of the pull of gravity on that mass.

• A force (usually due to gravity).

• If the force of gravity decreases, weight decreases.

• If the force of gravity increases, weight increases.

• Measured in newtons.

Mass

​But we are so much smaller than Earth, so the effect is greater on us. (Earth isn't affected by our gravitational pull, but Earth's gravity keeps us from floating away.)

Every object in the universe attracts every other object with a gravitational force.

The strength of the force depends on two things: mass and distance.