1. Universal Forces Chapter 12.4

2. Universal Forces Observations of planets, stars, and galaxies strongly suggest four universal forces exist throughout the universe. Electromagnetic Strong nuclear Weak nuclear Gravitational

3. Forces act over a distance between particles of matter: -The particles don’t need to be in contact -Forces are affected by the distance between the particles of matter

4. Electromagnetic Forces Electromagnetic force is associated with charged particles. Electric and Magnetic forces are the only forces that can both attract and repel

5. Electric Force Acts between charged objects or particles (electrons and protons) Objects with opposite charges attract each other Objects with like charges repel one another

6. Clothes often acquire electric charges in the drier. Cotton loses electrons easily = + charge Polyester gains electrons easily = - charge Clothes with opposite charges tend to cling together.

7. http://funny-pictures.feedio.net/static-electricity-cat-funny-picture-lol-meme/imglols.com*wp- content*main*2010_09*static-electricity-cat.jpg/

8. Magnetic Force Act on certain metals, poles of magnets, moving charges. http://www.b-ecochic.com/wooden-toy-train-set.html http://anjungsainssmkss.wordpress.com/category/sains-ting-3-form-3-pmr/chapter-7- electricity/

9. Nuclear Forces Two forces, strong nuclear and weak nuclear, act within the nucleus to hold it together. physics.tutorvista.com

10. Gravitational Force Gravitational force = an attractive force that acts between any two masses. Newton’s law of universal gravitation states that every object in the universe attracts every other object.

11. You exert a gravitational force on your book and your book exerts a gravitational force on you. You don’t notice this because the masses are so small. It takes a HUGE mass to exert a large gravitational force.

12. The gravitational force between two objects depends on their mass and distance. A: two masses, X & Y, attract each other B: larger mass of X results in larger gravitational force C: an increase in distance decreases the gravitational force

13. Gravity Gravity is the weakest universal force but is the most effective over large distances. Gravity: -Holds you on Earth -Keeps the moon in orbit around Earth -Keeps the planets in orbit around sun -Keeps stars in orbit in galaxies Gravity (minute physics)

14. The Moon How is the moon kept in orbit around the Earth? Moon has inertia: move along a straight path until acted on by a force (Earth’s gravitational pull) Centripetal force = center-directed force that continuously changes the direction of an object to make it move in a circle

16. Tides The gravitational pull from the moon produces two bulges in the Earth’s oceans. Earth rotates under these bulges which creates 2 high tides and 2 low tides each day. tides

17. Review 1.Which of the following is NOT one of the universal forces? a.Strong nuclear b.Gravitational c.Electromagnetic d.Magical

18. Review 2.Which forces are the only forces that can both attract and repel? a. electric and nuclear b. magnetic and nuclear c. magnetic and gravitational d. electric and magnetic

19. Review 3.The gravitational force between two objects depends on the objects’… a. masses and distance b. masses and weight c. distance and volume