gravity

1. GRAVITY

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

12. THANK YOU