Gravity

Scientists have observed the motion of falling objects and the
motions of planets for many years.

Although scientists could not see gravity, they could see its
effects.

Gravity is a force of attraction between objects due to their
mass.

Gravity is always an attractive force because it always pulls
objects towards each other.

Force is a push or a pull upon an object resulting from the
object’s interaction with another object.

What is weight?

Mass: is the amount of matter in an object

Weight: is a measure of the pull of the gravity on that mass. Weight is a force.

Our weight on Earth is how much force the Earth gravity has on us and how hard it
is pulling us towards the surface

Think of it this way.

An object is made up of a certain amount of matter, so its mass is constant.

The object has a certain weight due to the force of gravity.

If the force of gravity decreases, the weight of the object decreases. If the force of
gravity increases, the weight of an object increases.

Mass and Weight

A common unit for mass in the metric system is in grams (g) or kilogram (kg).

Scientist measure forces with newton (N), a unit named after Isaac Newton.

Ex. An apple with a mass of about 102g weighs 1N on Earth.