1. 1 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity

2. 2 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity * Gravity is a force of attraction that acts between two massive object

3. 3 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity * Gravity is a force of attraction that acts between two massive object * Two (massive) objects will exert a gravitational attraction with each other no matter how large or small the masses

4. 4 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity * Gravity is a force of attraction that acts between two massive object * Two (massive) objects will exert a gravitational attraction with each other no matter how large or small the masses * Gravity is a fairly weak force unless the masses are quite large

5. 5 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity * Gravity is a force of attraction that acts between two massive object * Two (massive) objects will exert a gravitational attraction with each other no matter how large or small the masses * Gravity is a fairly weak force unless the masses are quite large * First quantified by Newton

6. 6 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity * Gravity is a force of attraction that acts between two massive object * Two (massive) objects will exert a gravitational attraction with each other no matter how large or small the masses * Gravity is a fairly weak force unless the masses are quite large * First quantified by Newton * Inverse square Law

7. 7 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity * Gravity is a force of attraction that acts between two massive object * Two (massive) objects will exert a gravitational attraction with each other no matter how large or small the masses * Gravity is a fairly weak force unless the masses are quite large * First quantified by Newton * Inverse square Law * ‘Action at a Distance”

8. Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity

9. 9 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity m1m1 m2m2

10. 10 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity m1m1 m2m2 r

11. 11 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity F = G m 1 m 2 / r 2 m1m1 m2m2 r

12. 12 Motion – Newton’s Laws Gravity – A Closer Look The Universal law of Gravity F = G m 1 m 2 / r 2 G = 6.67 x 10 -11 N-m 2 / kg 2

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14. The Earth from Apollo 10

15. 15 Motion – Newton’s Laws Gravity – Why does g = 9/8 m/s 2 on the surface of the earth? F = G m 1 m 2 / r 2 m1m1 m2m2 r

16. 16 Motion – Newton’s Laws Gravity – Why does g = 9/8 m/s 2 on the surface of the earth? F = G m 1 m 2 / r 2 m1m1 m2m2 r

17. 17 Motion – Newton’s Laws Gravity – Why does g = 9/8 m/s 2 on the surface of the earth? F = G m 1 m 2 / r 2 Earth m1m1 m2m2 r r ≈ R earth m 1 = M earth

18. 18 Motion – Newton’s Laws Gravity – Why does g = 9/8 m/s 2 on the surface of the earth? F = G m 1 m 2 / r 2 = G M earth m 2 / R earth 2

19. 19 Motion – Newton’s Laws Gravity – Why does g = 9/8 m/s 2 on the surface of the earth? F = G m 1 m 2 / r 2 = G M earth m 2 / R earth 2 This is the force of gravity on m 2 and is, therefore, the weight of m 2.

20. 20 Motion – Newton’s Laws Gravity – Why does g = 9/8 m/s 2 on the surface of the earth? F = G m 1 m 2 / r 2 = G M earth m 2 / R earth 2 According tot the Second Law: F = G M earth m 2 / R earth 2 = m 2 a

21. 21 Motion – Newton’s Laws Gravity – Why does g = 9/8 m/s 2 on the surface of the earth? According to the Second Law: F = G M earth m 2 / R earth 2 = m 2 a Or, at the surface of the earth a = G M earth / R earth 2 = 9.8 m/s 2