CHAPTER 7 Gravitation
CHAPTER 7Gravitation
UNIVERSAL GRAVITATION
What is Newton’s Law of Universal Gravitation and how do I apply it?
DEVELOPMENT OF THE MODEL OF THE UNIVERSE
Original model?
Copernicus – 1543
Brahe – 1560
No telescopes, measurements over 20 years
KEPLER
Brahe’s assistant
Applied geometry to the data
Sun is in the center
Orbits are ellipse shaped
Planets move faster closer to the sun
NEWTON
The apple falls, where does this force come from?
How does this apply to the motion of planets?
NEWTON
Third Law
Can be thought of as a force of attraction
Directly proportional to the masses of the objects
Can also be called gravitational force
Newton’s Law of Universal Gravitation
LAW OF UNIVERSAL GRAVITATION
• Measures the force of attraction between any two objects
• As small as electrons, as large as planets
RELATIONSHIPS BETWEEN THE VARIABLES
Between F and m
Between F and r?
What if we double m1?
What if we double r?
INVERSE SQUARE LAW
According to Newton’s equation, F is inversely related to the square of the distance.
SOLVING FOR VARIABLES
F can be Fg
If so, solve for g
Application?
Solve for mE
EXAMPLE
Find g if r = 1.5 m, density = 3.3 x 103 kg/m3
What would happen if the prince jumped upward?
HOMEWORK
Page 191 # 55 – 60, 64
G ?!
100 years after Newton
Cavendish – 1798
Confirmed that there is a gravitational attraction between two objects
Enabled the calculation of the mass of the Earth
MEASURING G
Original spheres were lead
Worked for any materials
HOMEWORK
Worksheet