1. Chapter 4Linear motion

2. 1) Linear means in a straight line

3. 2) Describe the motion of an object by its position, speed, direction and acceleration

4. 3) Distance is a scalar. Distance is “how much ground is covered” during motion.

5. 4) Displacement is a vector Displacement is  X “final position – initial position”

6. 5) Example: distance is the path length from o to c

7. Example: distance is the path length from a to c

8. But displacement is the vector from a to c = final position – initial position

9. 6) Motion is relative. An object is moving if its position relative to a fixed point is changing.

10. 7) Example: A crate on a train traveling at 20 m/sec. The crate is at rest wrt the train. But the crate is moving 20 m/sec relative to the ground.

11. 8) Unless stated otherwise, we measure speed relative to the Earth.

12. 7) Speed is how fast an object is moving. Speed is a scalar quantity.

13. 10) From motion experiments, Galileo defined Speed = distance/time 11) Before Galileo, motion was simply described as “fast” or “slow”

14. 12) Instantaneous speed is the speed at any instant. 13) A speedometer shows instantaneous speed.

15. 11) Average speed = total distance time interval

16. 15) Velocity = speed in a given direction. Velocity is a vector quantity.

17. 16) Constant velocity = means same speed in same straight-line direction.

18. 17) Changing velocity : if either the speed changes or the direction changes or both change

19. 18) Acceleration is the rate of change of velocity acceleration is a vector. 19) acceleration = change of velocity time interval

20. 20) Deceleration = decrease in acceleration

22. 21) Accelaration for object traveling in a straight line = change in speed time interval

23. Free fall

24. 22) projectile: an object that moves only under the influence of gravity. 23) Free fall = object falling under influence of gravity.

25. 24) Trajectory = path of a projectile

26. 25) When we talk about free fall, we ignore air resistance.

27. 26) Acceleration of object in free fall is about g= 10 meters/sec 2

28. 27) Kinematics is the study of motion Galileo discovered these relationships.

29. 28) There are 6 kinematics variables and 2 kinematics equations

30. 29)Kinematics variables for free falling object, Y = final position in y direction Y o = initial position in y direction V oy = initial velocity in y direction V fy = final velocity in y direction a y = -g t = time elapsed

31. 30) What is meant by “-g”? The object is accelerating in the negative direction

33. 31) Kinematic Equations y = y o + v o t + ½ a t 2 V = v o + at x = x o + v o t + ½ a t 2 V = v o + at

34. 32) For freefall, equations simplify to y = - ½ g t 2 V = - gt

35. 33) Rising objects: an object thrown straight up will slow down, stop and fall back down

36. 34) At the highest point, the vertical velocity is zero.

37. 28) Projectile motions 1-D 1-D 2-D