Gravity and Motion

"What determines the strength of gravity between two objects?"

"What two factors combine to keep the moon and Earth in orbit?"

Gravity:

-a force that attracts all objects towards each other.

Newton’s Law of Universal Gravitation: 

Every object in the universe attracts every other object.

The strength of the force of gravity between two objects depends on two factors:

the masses of the two objects and their distance.

Gravity, Mass, and Weight

​Mass- the amount of matter an object has.  Mass never changes

Weight- the force of gravity on an object.  The weight of an object is determined by its location.  The higher force of gravity, the heavier you weight

Gravity and Distance: The closer the two objects are, the stronger the force of gravity.  The opposite happens as distance increases.

Which pair of objects has a great force of gravity?

Pair A?

or Pair B?

ANSWER: Pair A!

The closer the two objects are, the stronger the force of gravity.  

Pair A?

or Pair B?

Inertia and Orbital Motion

" What causes the planets to remain in orbit?"

Inertia- the tendency of an object to resist a change in motion.

Orbital Motion

Newton concluded that gravity and inertia combine to keep the Earth in orbit around the sun and the Moon in orbit around Earth.