1. Universal Gravitation Part 2

3. What holds galaxies together? Newton’s Law of Universal Gravitation says:

5. Gravitational Force The force exerted between two masses On Earth, we experience this force as weight Earth pulls on us with the same force we pull on Earth Which one is more likely to move? Why?

7. Henry Cavendish 1798 Used Cavendish balance to measure the value of G G= 6.67 x 10 -11 Nm 2 /kg 2

9. Problem What is the gravitational force between two 15 kg packages that are 35 cm apart? Known: m 1 =15 kg m 2 = 15 kg r= 0.35 m Equation: F = G m 1 m 2 r 2

10. Problem, Continued Put values in the equation F = (6.67x10 -11 Nm 2 /kg 2 )(15kg)(15kg) (0.35 m) 2 Solve F = 1.225 x 10 -7 N