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What is Kinematics? Geometry of motion

What is Kinematics? Geometry of motion. Kinematics is the study of the geometry of motion and is used to relate displacement, velocity, acceleration and time without reference to the cause of motion. The Language of Kinematics. Distance. Displacement. Velocity. Speed. Acceleration.

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What is Kinematics? Geometry of motion

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  1. What is Kinematics?Geometry of motion Kinematics is the study of the geometry of motion and is used to relate displacement, velocity, acceleration and time without reference to the cause of motion.

  2. The Language of Kinematics Distance Displacement Velocity Speed Acceleration

  3. The Language of Kinematics Scalar Quantities: Quantities that are fully described by magnitude alone. Ex: Temperature = 14 degrees F Energy =1500 calories Time = 30 seconds

  4. The Language of Kinematics Vector Quantities: Quantities that are fully described by BOTH a magnitude and a direction. Ex: Displacement = 1 mile, Northeast Velocity = 75 mph, South Force = 50 pounds, to the right (East)

  5. The Language of Kinematics Distance (d): Scalar Quantity How far an object has traveled during its time in motion. Ex: A person walking ½ mile to the end of the trail and then returning on the same route: the distance walked is 1 mile.

  6. The Language of Kinematics Displacement (s): Vector Quantity A measure of an object’s position measured from its original position or a reference point. Ex: A person walking ½ mile to the end of the trail and then returning on the same route: the displacement is 0 miles. S = 0

  7. End Start The Language of Kinematics Distance: length traveled along a path between 2 points End Start • Displacement: straight line distance • between 2 points

  8. End Y displacement Start X displacement The Language of Kinematics Displacement can be measured as two components, the x and y direction:

  9. The Language of Kinematics Speed: Scalar Quantity The rate an object is moving without regard to direction. The ratio of the total distance traveled divided by the time. Ex: A car traveled 400 miles for 8 hours. What was its average speed? Speed = 50 mph

  10. The Language of Kinematics Velocity (v): Vector Quantity The rate that an object is changing position with respect to time. Average Velocity is the ratio of the total displacement (s) divided by the time.

  11. The Language of Kinematics Velocity (v): Vector Quantity Ex: What would be the average velocity for a car that traveled 3 miles north in a total of 5 minutes?

  12. The Language of Kinematics Velocity (v): Vector Quantity Ex: What would be the average velocity of a car that traveled 3-miles north and then returned on the same route traveling 3-miles south in a total of 22 minutes?

  13. The Language of Kinematics Acceleration (a): Vector Quantity The rate at which an object is changing its velocity with respect to time. Average Acceleration is the ratio of change in velocity to elapsed time.

  14. The Language of Kinematics Acceleration (a): Vector Quantity Ex: What is the average acceleration of a car that starts from rest and is traveling at 50m/s (meters per second) after 5-seconds? • a = 50m/s – 0m/s a = 10 m/s2 • 5 sec

  15. Projectile Motion – Motion in a plane Motion in 2 directions: Horizontal and Vertical Horizontal motion is INDEPENDENT of vertical motion. Path is always parabolic in shape and is called a Trajectory. Graph of the Trajectory starts at the origin.

  16. Projectile Motion Assumptions Curvature of the earth is negligible and can be ignored, as if the earth were flat over the horizontal range of the projectile. Effects of wind resistance on the object are negligible and can be ignored.

  17. or Projectile Motion Assumptions • The variations of gravity (g) with respect to differing altitudes is negligible and can be ignored. • Gravity is constant:

  18. Projectile Motion First step: To analyze projectile motion, separate the two-dimensional motion into vertical and horizontal components.

  19. Projectile Motion Horizontal Direction, x, represents the range, or distance the projectile travels. Vertical Direction, y, represents the altitude, or height, the projectile reaches.

  20. Projectile Motion • Horizontal Direction: • No acceleration: therefore, ax= 0. • Vertical Direction: • Gravity affects the acceleration. It is constant and directed downward: therefore, ay = -g.

  21. = 0 t0 Projectile Motion At the maximum height:

  22. Projectile Motion Formulas • Displacement in general Professional Development Lesson ID Code: 5009

  23. Projectile Motion Formulas Horizontal Motion: The x position is defined as:

  24. Projectile Motion Formulas Horizontal Motion: Since the horizontal motion has constant velocity and the acceleration in the x direction equals 0 (ax = 0 because we neglected air resistance) , the equation simplifies to:

  25. Projectile Motion Formulas Vertical Motion: The y position is defined as:

  26. Projectile Motion Formulas Vertical Motion: Since vertical motion is accelerated due to gravity, ay = -g, the equation simplifies:

  27. Projectile Motion Formulas Initial Velocity (vi) can be broken down into its x and y components:

  28. Projectile Motion Formulas Going one step further: There is a right triangle relationship between the velocity vectors – Use Right Triangle Trigonometry to solve for each of them.

  29. 90° θ° Right Triangle Review: • Right triangle: • A triangle with a 90° angle. Hypotenuse, H Opposite side, O Sides: Hypotenuse, H Adjacent side, A Opposite side, O Adjacent side, A

  30. Trigonometric Functions: • Trigonometric Functions: • sin θ° = O / H • cos θ° = A / H • tan θ° = O / A

  31. Projectile Motion Formulas

  32. Projectile Motion Formulas

  33. Projectile Motion Formulas • Horizontal Motion: • Combine the two equations: and

  34. Projectile Motion Formulas • Vertical Motion: • Combine the two equations: and

  35. Projectile Motion Problem • A ball is fired from a device, at a rate of 160 ft/sec, with an angle of 53 degrees to the ground.

  36. Projectile Motion Problem • Find the x and y components of Vi. • At the highest point (the vertex) what is the altitude (h) and how much time has elapsed? • What is the ball’s range (the distance traveled horizontally)?

  37. Projectile Motion Problem Find the x and y components of Vi. Vi = initial velocity = 160 ft/sec

  38. Projectile Motion Problem Find the x and y components of Vi.

  39. Projectile Motion Problem Find the x and y components of Vi.

  40. Projectile Motion Problem At the highest point (the vertex), what is the altitude (h) and how much time has elapsed?Start by solving for time.

  41. Projectile Motion Problem At the highest point (the vertex), what is the altitude (h) and how much time has elapsed?Now using time, find h (ymax).

  42. Projectile Motion Problem What is the ball’s range (the distance traveled horizontally)? It takes the ball the same amount of time to reach its maximum height as it does to fall to the ground, so total time (t) = 8 sec. Using the formula:

  43. Projectile Motion Problem-2 A golf ball is hit at an angle of 37 degrees above the horizontal with a speed of 34 m/s. What is its maximum height, how long is it in the air, and how far does it travel horizontally before hitting the ground?

  44. Answers: • Maximum height: 21.44 meters • Total time in the air: 4.18 seconds • Horizontal Distance: 113.7 meters

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