1. Gravity

2. Gravity is a pulling force It pulls things down towards the earth

3. Things fall because of gravity

4. Things always fall down

5. Gravity was discovered by a scientist called Isaac Newton

6. Stories say he discovered Gravity when an apple fell on his head

7. What is gravity? Gravity is the force of attraction between any two objects.

8. Gravity holds everything and every one on the earth Even in Australia

9. In Space, Gravity keeps the planets moving around the sun

10. Gravity depends on: 1- Mass of an object 2- distance between objects

11. Earth’s gravitational acceleration Try to drop a science book and a paper at the same time, which would hit the ground first????????? (suppose there is no air resistance) Free falling object would fall with the same acceleration. Acceleration of gravity is 9.8m/s 2

12. According to Newton’s second law: Fnet= m x a What is the force of gravity exerted on an object?? F = m x acceleration of gravity F= m x g

13. Application What is the gravitational force on an object with a mass of 60 Kg? Find the force exerted by a rope on a 10 Kg mass that is hanging from the rope.

14. Weight Does gravity exert a force on you while you are sitting know thinking to find an answer for this question? The gravitational force exerted on an object is called weight. Because the weight of an object is equal to the Earth’s gravity on the object, weight can be calculated from this equation: W = m x g

15. Application On Earth, what is the weight of a large- screen TV that has a mass of 75 Kg Find the acceleration of gravity on Mars if a person with a mass of 60 Kg weighs 222N on Mars.

16. MASS  Mass is a physical property of matter that explains how much matter is in an object  Mass does not change when gravity changes WEIGHT  Weight is a force which is calculated by multiplying the acceleration of gravity times mass.  Weight can change when gravity changes Mass and Weight are two different Properties of Matter

17. An elephant on the Earth would weigh less on the Moon, because gravity is less on the moon. An elephant’s mass would not change if he went to the moon WEIGHT