1. Gravitation See video on extreme sports --- defying gravity
See video on Gravitation

2. Newton’s Law of Gravitation
Any two point masses
attract each other
with a force
that is proportional to each of their masses
and inversely proportional to the square of the distance between them.

3. average distance from the Earth to the Sun = 1.5  1011 m.
Data
G = 6.67  N m2 kg-2
mass of the Earth = 6.0  1024 kg
radius of the Earth = 6.4  106 m
mass of the Sun = 2.0  1030 kg
average distance from the Earth
to the Sun = 1.5  1011 m.

4. Questions
Page 123 Bath Advanced Science Physics

5. Gravitational Field Field lines never start or stop at empty space
Field lines never cross
Gravitational field strength at a point
is the force per unit mass
exerted on a mass placed at that point.

6. Questions
Page 126 Bath Advanced Science Physics

7. Work
Energy
Gravitational Potential Energy
Gravitational potential energy is energy an object possesses because of its position in a gravitational field

8. Potential
The potential at a point in a field as the gravitational potential energy per unit mass placed at that point in the field
Equipotentials join points of equal potential

9. Questions
Page 128 Bath Advanced Science Physics

10. Kepler’s Laws (see video)
All of the planets move in elliptical orbits with the Sun at one focus.

11. Kepler’s Laws (see video)
The radius vector (imaginary line between the Sun and the planet) sweeps out equal areas in equal times.