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Frame of reference

Frame of reference. Physical Definition- a framework that is used for the observation and mathematical description of physical phenomena 2 Simple definitions- 1. how an object experiences or views the motion; 2. object’s point of view. How do…. ….people account for a frame of reference?

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Frame of reference

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  1. Frame of reference • Physical Definition-a framework that is used for the observation and mathematical description of physical phenomena • 2 Simple definitions- • 1. how an object experiences or views the motion; • 2. object’s point of view

  2. How do… • ….people account for a frame of reference? Takes into account 2 objects: • The observer • The object being compared to the observer

  3. Consider this still person on the ground as the observer frame of reference, he is observing a plane in the sky • He see’s the plane going 100 km/hr Man’s Velocity = 0 km/hr

  4. Now… • Consider him moving in the opposite direction as the plane at a rate of 25 m/s, while observing the plane still. • Relative to the man, what is the plane’s speed? Man’s Velocity = 25 km/hr

  5. The speed is… • The absolute value of the difference in their two speeds, while considering their directions: • Since we are considering opposite directions, we compare them with + and – signs. Since they are opposites, identify one as + and one as - . • 25 km/hr – (-100 km/hr) = 125 km/hr • The relative speed of the plane with respect to the man is 125 km/hr

  6. Now… • Consider him moving in the same direction as the plane at a rate of 25 m/s, while observing the plane still. • Relative to the man, what is the plane’s speed? Man’s Velocity = 25 km/hr

  7. The speed is… • The absolute value of the difference in their two speeds, while considering their directions: • Since we are considering opposite directions, we compare them with + and – signs. Since they are opposites, identify one as + and one as - . • 25 km/hr – (100 km/hr) = - 75 km/hr • The relative speed of the plane with respect to the man is 75 km/hr

  8. Described with Vectors • More importantly, Vector Addition

  9. Speed/Velocity Vectors

  10. If motion does not fall in a straight line We use create a vector map, and use the Pythagorean Theorem to solve. a2 + b2 = c2

  11. Resultant Velocity The resultant velocity is the net velocity of an object with respect to a reference frame.

  12. -Relative Motion

  13. Example 1 • The white speed boat has a velocity of 30km/h,N, and the yellow boat a velocity of 25km/h, N, both with respect to the ground. What is the relative velocity of the white boat with respect to the yellow boat?

  14. Example 2- The Bus Ride A passenger is seated on a bus that is traveling with a velocity of 5 m/s, North. If the passenger remains in her seat, what is her velocity: • with respect to the ground? • with respect to the bus?

  15. Example 2 -continued The passenger decides to approach the driver with a velocity of 1 m/s, N, with respect to the bus, while the bus is moving at 5m/s, N. What is the velocity of the passenger with respect to the ground?

  16. Example 3- Airplane and Wind An airplane has a velocity of 40 m/s E. It is facing a headwind of 5m/s West. What is the resultant velocity of the airplane?

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