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Chapter 4 Linear motion

Chapter 4 Linear motion. 1) Linear means in a straight line. 2) Describe the motion of an object by its position, speed, direction and acceleration. 3) Distance is a scalar. Distance is “how much ground is covered” during motion.

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Chapter 4 Linear motion

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  1. Chapter 4 Linear 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 DX “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. Butdisplacementis 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/time11) 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 changesor both change

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

  20. 20) Deceleration = decrease in acceleration

  21. 21) Accelaration for object traveling in a straight line = change in speedtime interval

  22. Free fall

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

  24. 24) Trajectory = path of a projectile

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

  26. 26) Acceleration of object in free fall is about g= 10 meters/sec2

  27. 27) Kinematics is the study of motionGalileo discovered these relationships.

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

  29. 29)Kinematics variables for free falling object, Y = final position in y directionYo = initial position in y directionVoy = initial velocity in y directionVfy = final velocity in y directionay = -gt = time elapsed

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

  31. 31) Kinematic Equations y = yo + vot + ½ a t2V = vo + atx = xo + vot + ½ a t2V = vo + at

  32. 32) For freefall, equations simplify to y = - ½ g t2V = - gt

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

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

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

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