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# lecture2 - Chapter 2 Kinematics-1D Reference Frames Any...

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Chapter 2 Kinematics-1D

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Reference Frames Any measurement of position, distance, or speed must be made with respect to a reference frame. The object s position is its location with respect to the frame of reference Will use + and signs to indicate positions in front or in back of the reference point If you are sitting on a train and someone walks down the aisle, the person’s speed with respect to the train is a few miles per hour, at most. The person’s speed with respect to the ground is much higher.
Distance and displacement Distance: the length of a path followed by a particle, always positive. Displacement: change in position during some time interval Δ x = x f – x i Can be positive and negative We make a distinction between distance and displacement.

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Position-Time Graph ---- shows the motion of the particle (car)
Average Velocity and Speed The average velocity is rate at which the displacement occurs The average speed = total distance / total time is a scalar quantity, always positive The SI unit of velocity and speed is m/s v average = Δ x Δ t = x f x i Δ t

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Simple practice What are the average velocity and speed in the first 30 s?
Example The position versus time for a certain particle moving along the x axis is shown in Figure. Find the average velocity and speed in the time intervals (a) 0 to 2 s, (b) 0 to 4 s, (c) 2 s to 4 s, (d) 4 s to 7 s, and (e) 0 to 8 s. .

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Example A person walks first at a constant speed of 5.00 m/s along a straight line from point A to point B and then back along the line from B to A at a constant speed of 3.00 m/s. What is (a) her average velocity over the entire trip? (b) her average speed over the entire trip?
The limit of the average velocity as the time interval becomes infinitesimally short, or as the time interval approaches zero. The instantaneous velocity indicates what is

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lecture2 - Chapter 2 Kinematics-1D Reference Frames Any...

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