1. Gravity What is gravity?

2. Gravity Gravity is a force between ALL objects! Gravity

3. The size of the force depends on the mass of the objects. The more mass, the bigger the force! Small attractive force (small mass) Bigger attractive force (larger mass)

4. The size of the force also depends on the distance between the objects. The closer the distance, the bigger the force! Small attractive force (far) Bigger attractive force (close)

6. Everything with mass has a force of gravity, but we only really notice the gravitational attraction to big objects! Hola! ¿Como estas?

7. The force of gravity on something is called its weight. Because it is a force it weight is measured in Newtons. Weight

8. Gravity On the earth, Mr Hubeny’s weight is around 800 N. 800 N I love physics!

9. Gravity On the moon, his weight is around 130 N. Why? 130 N

10. Gravity In deep space, far away from any planets or stars his weight is almost zero. (He is weightless). Why? Cool!

11. Mass vs. weight Mass is a measure of the amount of material an object is made of. It is measured in kilograms. Weight is the force of gravity on an object. It is measured in Newtons. Since weight is a force, it is found with same formula for finding force: F =ma, but for weight we write as Fg = mg where g = acceleration due to gravity (10m/s 2 )

12. On the moon, and on Earth, Mr. Hubeny’s weight is different, but his mass is the same! Why???????????

13. Examples What is the weight of an object on Earth if its mass is 45 kg? (g Earth = 10m/s 2) Fg (N) = mass (kg) x g(m/s 2 ) Fg (N) = 45 kg x 10 m/s 2 Fg = 450 N Fg (N) = mass (kg) x g(m/s 2 ) Fg (N) = 45 kg x 2 m/s 2 Fg = 90 N What would the weight of the object be if it was on the moon ? (g moon = 2m/s 2)

14. If an object weighs 250N on Earth, what is its mass? Fg (N) = mass (kg) x g(m/s 2 ) Mass (kg) = F (N) / g(m/s 2 ) Mass (kg) = 250N /10 m/s 2 Mass = 25kg

15. Easy isn’t it? http://www.youtube.com/watch?v=coX1u2_KBsQ http://www.youtube.com/watch?v=HKdwcLytloU&feature=related https://www.youtube.com/watch?v=ya2vzagppVQ&feature=rela ted