Gravity Unit 6

Sir Isaac Newton

● Famous for contemplating a falling apple and the moon

○ If gravity made the apple fall to Earth, why doesn’t

the moon fall to Earth

● Law of Universal Gravitation

○ Force = mass1 X mass2 / Distance2

○ F = m1 X m2 / D2

The Universal Gravitation Constant

● A slight correction was needed to Newton’s formula

● This allows us to find the mass of any thing in the

universe!

Gravity and Weight

● Mass = amount of matter in an object

○ Kg

● Weight = force of gravity on an object

○ N (or pounds)

● Gravity is constantly pulling you towards the center of

the Earth

Weight and Weightlessness

● Weight depends

on gravity and
“not falling”

● Think of being in

an elevator

Weight and Weightlessness

● Astronauts

○ Are outside of Earth’s gravity
○ They are weightless
○ But still have the same mass

■ And the same inertia

Gravity

● Gravity is a force that pulls objects to the center of mass

○ You are being pulled towards the center of Earth
○ In space, two EVA astronauts are pulled towards

each other

● More massive objects have more gravity

Different Gravities

● Earth = 9.8 m/s2
● Moon = 1.6 m/s2
● Mars = 3.7 m/s2
● Jupiter = 24.8 m/s2
● Sun = 274 m/s2

Falling

● Earth’s acceleration of gravity = 9.8 m/s2

○ Sh, 32 ft/s2

● Very second an object falls, its velocity increases by 9.8

m/s

● Everything falls at the same rate (ignoring air

resistance)
○ A grape and a bowling ball falls at the same rate

Terminal
Velocity

●Air resistance
opposes movement
through air (drag)

●Terminal Velocity is
the fastest that an
object can fall
○Depends on
the size and
shape of the
object