MOTION IN ONE DIMENSION Distance Displacement Speed and

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MOTION IN ONE DIMENSION Distance, Displacement, Speed, and Average Velocity

MOTION IN ONE DIMENSION Distance, Displacement, Speed, and Average Velocity

What do you think? l l Would a book on your desk be in

What do you think? l l Would a book on your desk be in motion? Explain

Frame of Reference l Motion l l Frame of reference l l a change

Frame of Reference l Motion l l Frame of reference l l a change in position A point against which position is measured Example: A train traveling between stations l l It is in motion when measured against the track. It is stationary when measured against a seat.

Displacement ( x) l l Straight line distance from the initial position to the

Displacement ( x) l l Straight line distance from the initial position to the final position (change in position, x) Can be positive (+) or negative (-)

Displacement l What is the displacement for the objects shown? l Answer: 9 cm

Displacement l What is the displacement for the objects shown? l Answer: 9 cm l Answer: -15 cm

Displacement: Sign Conventions l Right (or east) ---> + l Left (or west) --->

Displacement: Sign Conventions l Right (or east) ---> + l Left (or west) ---> – l Up (or north) ----> + l Down (or south) ---> –

Average Velocity l Average velocity is displacement divided by the time interval. l The

Average Velocity l Average velocity is displacement divided by the time interval. l The units can be determined from the equation. l l SI Units: m/s Other Possible Units: mi/h, km/h, cm/year

Practice Problems l A car travels 36 km to the north in 30. 0

Practice Problems l A car travels 36 km to the north in 30. 0 min. Find the average velocity in km/min and in km/h. l l Answer: 1. 2 km/min to the north or 72 km/h to the north A car travels 100. 0 km to the east. If the first half of the distance is driven at 50. 0 km/h and the second half at a 100. 0 km/h, what is the average velocity? l Answer: 66. 7 km/h to the east

Speed l l l Speed does not include direction while velocity does. Speed uses

Speed l l l Speed does not include direction while velocity does. Speed uses distance rather than displacement. In a round trip, the average velocity is zero but the average speed is not zero.