1. The study of the interactions between matter and energy
Physics
The study of the interactions
between matter and energy

2. Isaac Newton
England 1642 – 1727

3. Isaac Newton 3 Laws of Motion optics – light and lenses gravity
motion of the planets
calculus
physics
3 Laws of Motion

4. Newton’s First Law of Motion (the Law of Inertia)
An object at rest will remain at rest FOREVER unless some force acts upon it
An object in motion will remain in motion in a straight line FOREVER unless some force acts upon it

5. Was Newton WRONG?
We pulled the books, they started moving, we let go, and just like Newton said they just kept on going……….no….wait…..

6. We stopped pulling, the books stopped. WHY?
Was Newton WRONG?
We stopped pulling, the books stopped. WHY?
Maybe Newton was wrong about force and motion
Or… maybe some force was changing the motion of the books!

7. There are NOT as many forces as you might think
Different forces
There are NOT as many forces as you might think
gravitational
All atoms attracted to all other atoms
atomic
P+, n0 and e- over VERY short distances
mechanical
Matter touching matter
electromagnetic
Opposites attract and likes repel

8. When analyzing forces, we draw arrows called VECTORS
An arrow works perfectly because a force can only act in one direction
VECTORS show us the direction and magnitude (strength) of the forces

9. Friction

11. There is NO SUCH THING as a perfectly smooth surface.
What causes Friction?
There is NO SUCH THING as a perfectly smooth surface.
Under a microscope we see that atoms and molecules stick out and make bumps and grooves on every surface

12. Walnut Leaf shown through an electron microscope

13. Glass under an electron microscope

14. Wherever matter touches matter there will be friction.
When two surfaces try to move across each other, the bumps and grooves get caught on each other THAT’S FRICTION!
Wherever matter touches matter there will be friction.

15. Uses of friction Friction allows us to CONTROL motion
When moving objects, friction makes it harder to move them.
Friction turns work energy into HEAT

16. Friction turns work energy into HEAT
Uses of friction
Friction turns work energy into HEAT

17. Wherever matter touches matter, there will be friction AND HEAT.
Controlling Friction
Wherever matter touches matter, there will be friction AND HEAT.
It can NEVER truly be eliminated, but there are some things that can change the friction

18. Keep the surfaces from touching
Controlling Friction
Smooth Surface
Make the bumps smaller
Lubricant
Fill in the grooves, put a layer between surfaces
The bumps and grooves roll across instead of getting snagged
Wheels or rollers
Keep the surfaces from touching
Use air, magnetism or magic

19. Do forces always change motion?
What happens here?

20. Do forces always change motion?
What happens here?

21. Net force – the force that is left after all the forces are calculated
If the net force is 0, there is no change in motion!

22. 10N
10N

23. 10N 4N

24. 5N
10N 5N 5N
10N 3N

25. What happens to the speed of this cart?