1. Chapter 4 Section 2 Part 1 of 2

2. Define Gravity: _________________________________________ _________________________________________ _________________________________________ _________________________________________ _________________________________________

3. Define Gravity: Gravity is an attractive force between any two objects that depends on the masses of the objects and the distance between them.

4. Gravity is one of four basic forces. What are the other three? ________________________

5. Gravity is one of four basic forces. What are the other three? Electromagnetic Strong Nuclear Weak Nuclear

6. Isaac Newton formulated the law of universal gravitation, which he published in 1687. This law can be written as the following equation:

7. Isaac Newton formulated the law of universal gravitation, which he published in 1687. This law can be written as the following equation: In this equation G is a constant called the universal gravitational constant, and d is the distance between the two masses, m1 and m2.

8. Lets look at some examples for F=Gm 1 m 2 : d 2 9.8m (3kg) (2kg) = 14.7N s 2 (2m) 2 Reduce the distance: 9.8m (3kg) (2kg) = 58.8N s 2 (1m) 2 Reduce the mass: 9.8m (1kg) (2kg) = 4.9N s 2 (2m) 2

9. According to the law of universal gravitation, the gravitational force between two masses ___________ rapidly as the distance between the masses __________ No matter how far apart two objects are, the gravitational force between them never completely goes to zero.

10. According to the law of universal gravitation, the gravitational force between two masses decreases rapidly as the distance between the masses increases. No matter how far apart two objects are, the gravitational force between them never completely goes to zero.

11. In the 1840s the most distant planet known was Uranus. The motion of Uranus calculated from the law of universal gravitation disagreed slightly with its observed motion. Some astronomers suggested that there must be an undiscovered planet affecting the motion of Uranus. What was the name of this planet?

12. In the 1840s the most distant planet known was Uranus. The motion of Uranus calculated from the law of universal gravitation disagreed slightly with its observed motion. Some astronomers suggested that there must be an undiscovered planet affecting the motion of Uranus. What was the name of this planet? As a result of these calculations, the planet Neptune was found in 1846.

13. What is it when all forces except gravity acting on a falling object can be ignored? _________________ The acceleration of a falling object in free fall is about ________ given the symbol g and is sometimes called the _______________________________ By Newton’s second law of motion, the force of Earth’s gravity on a falling object is the object’s mass times the acceleration of gravity. We call this _______________________

14. What is it when all forces except gravity acting on a falling object can be ignored? Free fall The acceleration of a falling object in free fall is about 9.8 m/s 2 given the symbol g and is sometimes called the acceleration of gravity. By Newton’s second law of motion, the force of Earth’s gravity on a falling object is the object’s mass times the acceleration of gravity. We call this weight.

15. If a 10 kg object falls from the Empire State Building, what is the gravitational force on the object? HINT remember G is an acceleration so you have F and A Use F=MA

16. If a 10 kg object falls from the Empire State Building, what is the gravitational force on the object? HINT remember G is an acceleration so you have F and A Use F=MA What we know: M= 10kg A= 9.8 m s 2 Use the formula: (10kg)(9.8m/s 2 )=98kg m/s 2 Which we know is 98N

17. What equation would we use to find weight?

19. Weight and mass are not the same describe each. Weight is __________________________________ _________________________________________ Mass is ___________________________________ _________________________________________ __________________________________________ Example:

20. Weight and mass are not the same describe each. Weight is a force (the gravitational pull) based on how much mass an object has. Mass is how much matter is packed into an area. Example: More marbles more “stuff” more mass; which then leads to more gravitational pull or weight.

21. The weight of an object can change, depending on the gravitational force on the object. The table shows how various weights on Earth would be different on the Moon and some of the planets.