Answer these questions…

1. Answer these questions… • Why doesn’t earth fly off into space? • Where is Gondwanaland? • How do airplanes stay in the sky? • How much do you weigh in a pool of water?

2. Notes: Speed, Velocity and Acceleration

3. How do you know if an object is in motion? • It’s distance from another object is changing • The other object is the reference point ( a place or object used for comparison to see if an object is moving)

4. How do you describe motion? • Distance – How far it goes (measured in meters) • Speed – How fast it goes • Time – How long it takes to get there • Formula for Speed = Distance/Time • Example: 50 miles per hour

5. Constant Speed • Constant Speed – When an object’s speed is the same at all times during it’s motion • Example – an ship traveling across the ocean may move at the same speed for several hours • Long Distance Swimmers/Runners – keep the same pace for a certain part of the race • Practice Problem: A train travels at a constant speed of 80 miles in 2 hours. What is it’s speed?

6. Average Speed • Most objects do not move at the same speed for the entire time that it is in motion. • Example: A cyclist may glide over level ground, climb slowly up a hill, speed down hills • Practice Problem: A car is driven 60 miles in 2 hours and 100 miles during 4 hours. What is the car’s average speed?

7. Velocity • Speed in a given direction • Example – 4 meters per second North • Who would use velocity in their careers? • How would they use velocity?

8. Earth’s plates move in various directions very slowly Pangaea – super continent Laurasia – Northern mass of super continent Gondwanaland – Southern mass of super continent Theory of Plate Tectonics http://pubs.usgs.gov/publications/text/historical.html http://library.advanced.org/17701/high/pangaea/

9. Figure this one out… • Suppose scientists discover that a plate will move 5 centimeters per year. • Can you predict how far the plate will move in 1,000 years? • How far will the plate move in a day?

10. Alexander du Toit (1878-1948) Believed that Pangaea broke apart into 2 super-continents – Laurasia and Gondwanaland Alfred Wegener (1880-1930) Developed Theory of Pangaea

11. A change in velocity -either increasing speed, decreasing speed or changing direction Acceleration = (Final Velocity – Initial Velocity)/Time Acceleration

12. Figure this one out… • A roller coaster picks up speed as it rolls down a slope. • As it starts down the slope it’s speed is 4 meters/second, but 3 seconds later it’s speed is 22 meters/second. • What is the average acceleration?

13. When you travel in a car, where do the pushes and pulls you feel come from? When you experience pushes/pulls associated with acceleration, you continue the motion you had BEFORE the acceleration began. Check out the go-kart picture Explain This…

14. To Make Motion Graphs Easier: • A straight line means constant speed. • A horizontal line means no motion, 0 speed. • A positively sloped line means motion away from the reference point, + velocity • A negatively sloped line means motion toward the reference point, - velocity • A steeper slope = faster speed.

15. To Make Motion Graphs Easier: • The value of the slope is defined by the graphed units of time and distance • A curved line means a change in speed. • The rate of curvature defines the amount of acceleration.

16. Demonstration • What affects the acceleration of an object? • Which student moves faster? • Which student moves further? • Which student stays in place?

17. Why did this happen? • Objects with a larger mass have a greater resistance to acceleration. • Inertia – the tendency of an object to resist changes in motion • Force – a push or pull (sometimes results in motion)

18. Demonstration – Penny Activity • What will happen to the penny if you YANK the card out from under it? Yikes!!! Help Me!!

19. Why did this happen? • What actually happened? You caused the card to accelerate horizontally. • Why did this happen? The force was applied to the card only – Inertia kept the coin from moving. • Do you think it would be different if you pulled it slowly? It should go with the card everytime.

20. Who is Isaac Newton? • An English mathematician that discovered the three laws of motion.

21. An object remains in motion or at rest unless acted on by a force Newton’s First Law

22. Balanced Forces – all the forces acting on an object cancel each other out Unbalanced Forces – when there is a greater force in some direction causes movement Balanced vs. Unbalanced Force

23. A force that resists motion between two objects in motion that are touching Example – a runner’s shoes and the running surface Ice – not enough friction Mud – too much friction Example – air hockey table Friction

25. There are three types of friction

26. Sliding Friction • When two objects are rubbing against each other

27. Rolling Friction • The friction that exists when a wheel turns on a surface. • Caused by the small indentations created as one surface rolls over another • Resists slipping and spinning

29. Fluid Friction • The friction on a solid object as it moves through a liquid or gas

30. Gravity • A force that pulls free falling objects to earth’s center • All objects accelerate downward at a rate of 9.8 m/s2 (meters/second squared)

34. Demonstration – Money, Money • Do all objects fall at the same rate? • Which would fall faster a book or a dollar bill? • Why? • How can we get them to fall at the same rate?

35. Why did this happen? • As objects fall, more massive objects are more attracted to the earth but are also harder to accelerate (because of inertia) • Their inertia reduces their acceleration by exactly half as much as their greater attraction increases it

36. Mass – the amount of matter in an object Greater mass = greater inertia So mass= the amount of inertia in an object Weight – the gravitational pull of an object toward the earth What is the difference between mass and weight?

38. Overhead 6 Newton’s 2nd and 3rd Law

39. The force of an object is equal to the product (think math – what is a product) of its acceleration and its mass Force = Mass x Acceleration Force is Measured in Newtons Mass – usually in Kg Acceleration = m/s2 Newton’s Second Law

41. Think about it… • Since weight is a force you can rewrite Newton’s second law: • Weight = mass x acceleration

42. Newton’s Third Law • For every action force there is an equal and opposite reaction force.

45. Action Force – a push on something Reaction Force - the force that pushes back Example – balloon, fire hose, bullet fire, passing gas in the bath tub  Action vs. Reaction Force

46. Newton’s Third Law Cont. • How many objects is Newton talking about in his third law? • Can Action and Reaction forces be added together? • No • Why or Why not? Because they are acting on different objects

47. Figure Skaters – one skater pushes against the other – both move Squid – pushes water out - he moves forward Examples

48. BUT…. • Remember the roller chairs…. • Who moved further? • Speed and amount of movement when 2 objects are in contact depends on mass.

49. Another Example • If forces are equal in strength but in opposite directions then they cancel each other out.