1. CHAPTER 2: MOTION

2. WHAT IS MOTION? Motion is a change in an object’s position relative to some reference point

3. CHANGE IN POSITION 2 Different terms 1.Distance How far (in meters) that something has moved 2.Displacement Distance PLUS direction Relative to starting point

4. PROBLEM-SOLVING STRATEGIES 1.Read the problem. All of it, all the way to the end. 2.Draw a picture. This will be critical for some problems! a.Label everything 3.Identify what you are trying to solve. a.Write down knowns and unknowns b.Find an Equation that includes these values (if needed) 4.Solve the problem 5.Round to 1 decimal place, unless otherwise noted. 6.Put answers in scientific notation if they are more than 3 digits. 7.Make sure to include units!

5. EXAMPLES 1.The woman ran 5 meters north, 2 meters east, 5 meters south, and then 2 meters west. a)What was her distance traveled? b)What was her displacement?

6. TO SOLVE PROBLEM We read the problem. Let’s draw a picture. Identify what we are trying to solve Distance-how far she’s moved Displacement-how far relative to starting No equation needed Solve problem Distance:5m+2m+5m+2m=14m Displacement=?

7. ADDING DISPLACEMENTS Rules: 1.Add displacements in the same direction 2.Subtract displacements in opposite directions 3.Displacements that are not in the same or opposite directions cannot be directly added together.

8. BACK TO OUR PROBLEM 5m North-5m South=0m 2m East-2m West=0m Total: 0m+0m=0m

9. GUIDED PRACTICE To get to school from his house, Bobby walks 2 meters south and 3 meters west. What is his distance traveled? What is his displacement?

10. DISTANCE

11. DISPLACEMENT

12. YOU TRY IT To get to school, you leave your house and walk 4m east and 4m south. What is your distance from home? What is your displacement? Distance=10m Displacement=5.7m

13. SPEED

14. EXAMPLE PROBLEM

15. GUIDED PRACTICE If the speed on a highway is 30m/s and a car travels 100 meters in 3 seconds, are they speeding? K: d=100m, t=3s U:s=? E:s=d/t Solve: s=100m/3s S=33.3m/s They are speeding

16. YOU TRY IT How far does a car travel in 2 hours if it is moving at a constant speed of 20m/s? 40 km

17. TRIANGLE METHOD-NOT IN YOUR NOTES When you are given an equation where there is a fraction on one side and a single variable on the other, you can make them into a triangle. S=d/t Cover the variable that you are looking for, and your equation will be revealed. d=st You should still know the algebra, but can use this trick if helpful

18. CONSTANT SPEED VS CHANGING SPEED Constant speed: neither slowing down nor speeding up Changing speed: slowing down and speeding up We cannot solve this, so we need something else: Average speed: total distance and total time This is what we are solving. Instantaneous speed: The speed at a certain time (when you look at your speedometer)

19. GRAPHING MOTION Distance vs. time graph Independent variable=time Dependent variable=distance The slope of the line is the speed

20. VELOCITY

21. VELOCITY VS. SPEED You can be traveling at the same speed, but have a different velocity. Traveling around a curve at a constant speed-speed is constant, but velocity changes as the direction changes. Escalators

22. RELATIVE MOTION The choice of reference point affects how you describe motion See pg 53

23. MOMENTUM The product of an object’s mass and velocity Represented by letter “p” p=mv Let’s derive the units… p=mv Units for m=kg Units for v=m/s p=kg*(m/s) Always has a number and a direction

24. EXAMPLE PROBLEM A 90 kg running back is moving up the field (north) with a velocity of 10 m/s. What is his momentum? Knowns: mass (90kg) velocity (10.0 m/s north) Looking for: momentum (p) Equation: p=mv P=(90kg)*(10.0m/s north) =900kg*m/s north

25. GUIDED PRACTICE A 40 kg student walks 10 meters in 5 seconds. What is her momentum? Known: mass (40kg), distance (10m), time (5 sec) Unknown: momentum Equation: p=mv We don’t have the velocity! But we know how to get it… V=d/t =10m/5sec=2m/s P=(40kg)*(2m/s) =80kg*m/s forward

26. YOU TRY IT! An asteroid with mass 3*10 8 kg is heading for Earth with a velocity of 3*10 4 m/s. When it hits Earth, what is its momentum? 9-10 12 kg*m/s towards Earth

27. COMPARING MOMENTUMS Which has more momentum: a car traveling 30m/s or a semi traveling 30m/s? Why? P=mv The velocities are the same, but the mass of the semi will give it more momentum.

28. ACCELERATION The rate of change of velocity. Because velocity includes a direction, acceleration can be a change in direction OR velocity. Acceleration can be positive, negative, or zero. When an object speeds up, the acceleration is POSITIVE When an object slows down, the acceleration is NEGATIVE When there is no change in velocity, the acceleration is ZERO

29. IN DISTANCE V. TIME GRAPH, THE SLOPE IS THE ACCELERATION.

30. CALCULATING ACCELERATION

31. DELTA-NOT IN YOUR NOTES

32. EXAMPLE PROBLEM

33. GUIDED PRACTICE

34. YOU TRY IT

35. MOTION IN 2 DIMENSIONS Circular motion: When an object is moving in a circular path, the speed remains constant but it is accelerating because of the motion changes Velocity is perpendicular to the inward acceleration. This “center seeking” acceleration is called centripetal acceleration Ex. Carousel

36. PROJECTILE MOTION When you throw an object, gravity pulls it downward. It follows a curved path

37. THROWING AND DROPPING Will a bullet dropped or a bullet fired hit the ground first? http://www.teachertube.com/video/myth-busters-dropped-vs-fired-bullet- 235668 http://www.teachertube.com/video/myth-busters-dropped-vs-fired-bullet- 235668