The document discusses Newton's law of universal gravitation and how it applies to satellites orbiting Earth. It explains that satellites stay in orbit due to gravity, and that their orbital speed and period can be calculated using gravitational equations. The document also discusses weightlessness in space, the two types of mass, and Einstein's theory of relativity as it relates to gravity.

1. SECTION 7.2
Using the Law of Gravitation

2. USING THE LAW OF UNIVERSAL GRAVITATION
 What is Newton’s Law of Universal Gravitation and
how do I apply it?

3. SATELLITES
 GPS
 Cable
 Weather
 What is the shape of
their orbit?
 What force comes to
mind?

4. HOW DO THEY STAY UP?
 Discovered before we even had satellites by
Newton
 Giant Cannon

5. ORBITAL PERIOD


6. VELOCITY OF A SATELLITE


7. EXAMPLE
 A satellite orbits Earth
225 km above its
surface. What is the
orbital speed and
period?

8. HOMEWORK
 Page 181
 # 12 - 14

9. MORE NLUG
 How do I describe weightlessness?
 How do I describe gravitational fields?

10. MINI-LAB

11. FINDING ACCELERATION DUE TO GRAVITY


12. GRAVITATIONAL FIELD
 Is gravity a contact force?
 Michael Faraday developed the theory of field
forces when applied to magnetism
 Also applies to gravity

13. GRAVITATIONAL FIELD


14. EARTH’S GRAVITY
 Based on the
equation, what
happens to g as we
move away from the
Earth?

15. EXAMPLE
 Space shuttle orbits 4000 km above the Earth.
What is g at this height?

16. WEIGHTLESSNESS
 So if there is gravity, why do astronauts float?

17. WEIGHTLESSNESS
 We experience weight because of the normal force
pushing back on us
 Earth is providing the gravity
 In space, everything is experiencing the same
acceleration due to gravity
 So, no normal force

18. HOMEWORK
 Page 192
 # 72 - 78

19. TWO KINDS OF MASS
 How can I describe and measure the two different
types of mass?

20. INERTIAL MASS
 Using Newton’s
second:
 m = F/a
 Resistance to
movement

21. GRAVITATIONAL MASS


22. ALBERT EINSTEIN
 Said that inertial and gravitational mass are the
same
 Principle of equivalence
 So far has held true
 Basis in the theory of gravity

23. EINSTEIN’S THEORY OF GRAVITY
 Gravity is not a force, but
an effect of space itself
 Mass changes the space
around it
 Mass causes space to be
curved, and other bodies
are accelerated because
of the way they follow this
curved space.

24. DEFLECTION OF LIGHT
 Einstein’s theory
predicts the deflection
or bending of light by
massive objects
 Light follows the
curvature of space
around the massive
object and is deflected.

25. BLACK HOLE
 If an object is large enough, light cannot escape
 Black Hole
 Have been identified by their effect on nearby stars

26. HOMEWORK
 Page 193
 #80 - 85