Gravity EquationF = force of gravityG = gravitational constant (6*10-11) 0.00000000006

M1 = mass of body 1

M2 = mass of body 2S2 = distance between

M1 & M2 squared

F = M1* M2

S2G

Web

Gravity

1. The force of gravity is not effected by other bodies present.

2. The force of gravity is equal but oppositely directed.

F=ma Newton’s second law

F = M1* M2

S2G

Gravity

F = M1*M2

S2

M1A1 M2A2

M1A1 = M2A2

M2 is larger than M1

so, A1 must be larger than A2 if they are equal.

If the force is equal and opposite, then:

=

[Across a crowded room, you and an airplane]

G F

M2M1

F = MA for both

Web

Gravitational Constant

G ~ 6*10-11 - a very small number0.00000000006

What is the attraction between you and the person next to you?

What is the attraction between you and the earth?

F = M1* M2

S2G

Gravity

F = M1*M2

S2G

If masses stay the same, but the distance increases,

how does the force of gravity change?

M same

S increases= F <

Gravity

F = M1*M2

S2G

If distance stays the same, but the masses increase,

how does the force of gravity change?

increase

same= F >

Gravity

Will a body always have the same mass if the volume remains constant? NO

Same volume (size)

Density may be different, so masses are different

Venus (0.95 radius of earth, density 0.53)

Acceleration due to Gravity (g)

The acceleration of a body arising from the earth’s gravitational pull.

Units are ft/sec2 or m/sec2

At the earth’s surface g is: 9.8 m/sec2

or 32 ft/sec2

(g) depends on position

Web

Acceleration due to Gravity (g)

A body falling will continue to accelerate until air friction causes the body to reach a terminal velocity.

Acceleration due to gravity is independent of mass

Mass

ForceonAccelerati F = M A

The Beam Balance and Weight

Gravity

Known mass unknown mass1 kg ?

Weight = pull of gravity (a force)

[ Will it work everywhere? on Earth, another planet? in space? ]

Weight

Weight is the force of gravity between me and the earth.

1. How can I reduce my weight?

A) move scales to second floor?

B) move to the mountains?

F = M1*M2

S2G

Gravity and the Earth

F = M1*M2

S2G

N

S

N

S

-Rotates west to east-Velocity greater at equator, zero at poles-Centrifugal force bulges earth at the equator

-So, the earth is slightly squashed at equator

-equator diameter is 42 km > than pole diameter

diameter

Web