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Kinematics

Learn about the different types of motion, including translational, circular, and rotational, and how displacement and distance are used to measure the movement of objects.

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Kinematics

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  1. Kinematics describes the motion of objects

  2. Motion Motion is the movement of an object from one point in space to another point in space

  3. Motion in One Dimension Motion in one direction (translational motion)

  4. Motion in One Dimension Motion in one direction (translational motion) movement along a straight line

  5. TERMS: Mechanics is the study of motion of objects and the related concepts of force and energy Kinematics describes the motion of objects in motion Dynamics explains how forces cause changes in the motion of an object

  6. Motion An object’s motion can follow one of three paths • Translational: motion along a straight line, motion in 1 dimension • Circular: motion of an object along a curved path, 2 dimensional motion • Rotational: motion of a rigid body around an axis

  7. Modeling Translational Motion Idealized particle is used to model motion it has no volume, its size is not significant Compares to a mathematical point

  8. Frame of Reference • Any measurement of position, displacement, or speed requires a frame of reference • a point of comparison • Example • Have a student describe his precise present location without a frame of reference

  9. Frame of Reference • Any measurement of position, displacement, or speed requires a frame of reference • a point of comparison • Example • Have a student describe his precise present location without a frame of reference IT IS NOT POSSIBLE

  10. Displacement • Displacement is the movement of an object from one position to another. • Describes how far an object moves from its starting point.

  11. Displacement • Displacement is the movement of an object from one position to another. • Describes how far an object moves from its starting point. It requires a frame of reference

  12. Displacement • Displacement is the movement of an object from one position to another. • Describes how far an object moves from its starting point. It requires a frame of reference It also requires a direction to be specified up down left right North, South, East, or West other direction references

  13. Displacement • Displacement is the movement of an object from one position to another. • Describes how far an object moves from its origin (starting point) It requires a frame of reference It also requires a direction to be specified up down left right North, South, East, or West (distance; the distance an object travels without a reference to the direction)

  14. Distance • A ball rolled 5.0 m

  15. Distance • A ball rolled 5.0 m (no direction) • This statement is specifying a distance No direction is given ball may have rolled in any direction including up, or down a slope

  16. Displacement • A ball rolled 5.0 m towards the wall

  17. Displacement • A ball rolled 5.0 m towards the wall • This is a statement of displacement A direction is given--- towards the wall

  18. Displacement • A ball rolled 5.0 m to the left. • This is a statement of displacement A direction is given--- left

  19. Displacement • In Physics a coordinate axes is often used to represent a frame of reference

  20. Displacement • In Physics a coordinate axes is often used to represent a frame of reference Displacement of an object along the x axis is represented by ΔX

  21. Displacement • In Physics a coordinate axes is often used to represent a frame of reference • An object moves 70 m to the west and then moves 30 m to the east

  22. Displacement • In Physics a coordinate axes is often used to represent a frame of reference • An object moves 70 m to the west and then moves 30 m to the east • What is the displacement of this object?

  23. Displacement

  24. The object is displaced 40 m to the west of its origin

  25. The object is displaced 40 m to the west of its origin Notice that the 70m, 30m, and 40m length are approximately drawn to scale

  26. What distance did the object move?

  27. The object moved a distance of 100 m

  28. Displacement DISPLACEMENT is a VECTOR

  29. Displacement • In Physics a coordinate axes is often used to represent a frame of reference DISPLACEMENT is a VECTOR Vectors will be discussed in detail at a later time

  30. Displacement • The east – west displacement occurred on the X axis of the graph Displacement of an object along the x axis is represented by ΔX ΔX = X 2 - X1 X1 = the origin (initial position) of the object being displaced X2 = the final position of the object being displaced

  31. Displacement The displacement of the object in this slide is ΔX = X 2 - X1 ΔX = 30m – 10m = 20m The direction of this displacement is in the + X direction

  32. Displacement The displacement of the object in this slide is ΔX = X 2 - X1 ΔX = 10m – 30m = -20m The direction of this displacement is in the - X direction

  33. Average Velocity • Average speed is not the same as average velocity. • Average speed is the change in distanceover the change in time • Average velocity is the change in displacement over the change in time

  34. Average Speed • Average Speed: • Has no direction • A person driving a car might state that his speed is 45mph • he will have traveled 45 miles in 1 hour • It could be in a: • circle • straight line • crooked path • towards any point on the compass

  35. Average Speed • Average Speed = • Distance, by definition does not have a direction. Speed is not a vector • Average Speed is not often used in our physics course.

  36. Average Velocity • Average Velocity= = • displacement has a direction • so velocity must also have a direction

  37. Average Velocity • Average Velocity= • Average velocity is the rate of travel from a designated starting point (origin) TO a designated finishing point

  38. Average Velocity • Average Velocity= • Average velocity:the rate of displacement

  39. Average Velocity • Average Velocity= • The path taken may not be a straight line but the measure of displacement will be a straight line

  40. origin distance traveled Final Position

  41. origin distance traveled displacement Final Position

  42. Instantaneous Velocity The velocity of an object for a very short period of time Instantaneous Velocity = Δ time is approaching zero v = vdoes not have a line over it

  43. Velocity • Most of our velocity problems will pertain to average velocity

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