2. GRAVITY DEFINED
Gravity is the tendency of objects
with mass to accelerate towards
each other
Gravity is one of the four
fundamental forces (interactions)
in nature.
3. THE HISTORY OF GRAVITY
Sir Isaac Newton
theorized the
Law of Gravitation in
1687
4. UNIVERSAL GRAVITATION
Newton’s idea was that gravity was a universal
force acting between any two objects
Universal law of gravitation states that
every body attracts every other body
with a force. This force is directly
proportional to the product of their
masses and inversely proportional to the
square of the distance between them.
5. LAW OF UNIVERSAL GRAVITATION
In symbols, Newton’s Law of Universal
Gravitation is:
Fgrav = GMm
Where G is a constant of
proportionality.
G = 6.67 x 10-11 N m2/kg2
r 2
6. AT THE EARTH’S SURFACE
Newton knew that the gravitational
force on the apple equals the apple’s
weight, mg, where g = 9.8 m/s2.
W = mg
7. THE APPLE & THE MOON
Isaac Newton realized that the motion of a
falling apple and the motion of the Moon
were both actually the same motion,
caused by the same force - the
gravitational force
8. GRAVITY AND OUR SOLAR SYSTEM
The Sun’s gravity is what holds
our solar system together
Since Jupiter is the largest planet,
it has the most gravity.
Pluto has the least amount of
gravity of all the planets
9. MASS AND WEIGHT ARE TWO DIFFERENT
PROPERTIES OF MATTER
MASS
Mass is a physical property of matter that explains how much
matter is in an object
Mass does not change when gravity changes
WEIGHT
Weight is a force which is calculated by
multiplying the acceleration of gravity times
mass.
Weight can change when gravity changes
10. IF YOU PULLED A MOUSE AND AN
ELEPHANT WITH THE SAME
AMOUNT OF FORCE, THE
ELEPHANT WOULD RESPOND
LESS TO PULLING EVEN IF HE
DIDN’T PULL BACK AT ALL
THAT IS BECAUSE AN ELEPHANT
HAS MORE MASS THAN A MOUSE
MASS
11. An elephant on the Earth
would weigh less on the Moon,
because gravity is less on the
moon.
An elephant’s mass would not
change if he went to the moon
WEIGHT
