PHY101_Chap2Fall09

# PHY101_Chap2Fall09 - Chapter 2 2.1 Displacement Motion in...

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Chapter 2 Motion in One Dimension Motion: an ingredient in everything in physics. Depends on displacement, velocity and acceleration 2.1 Displacement

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2.1 Displacement • Defined as the change in position • f stands for final and i stands for initial – May be represented as Δ y if vertical – Units are meters ( m ) in SI, centimeters ( cm ) in cgs or feet ( ft ) in US Customary
Displacement or distance? Start from your dorm room to attend this class in Knox and return back to your dorm room after the class. The distance between your dorm and NSC is 1 mile. Your total displacement is 1. 2 miles 2. 1 mile 3. 0 mile

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Displacement Isn’t Distance • The displacement of an object is not the same as the distance it travels Example: Throw a ball straight up and then catch it at the same point you released it • The distance is twice the height • The displacement is zero
Position of car at various times

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Vector and Scalar Quantities • Vector quantities need both magnitude (size) and direction to completely describe them ( number and sign ) – Generally denoted by boldfaced type and an arrow over the letter – + or – sign is sufficient for this chapter • Scalar quantities are completely described by magnitude only ( only number )
Moving truck A truck moves 70 m east, then moves 120 m west, and finally moves east again a distance of 90 m. If east is chosen as the positive direction, what is the truck’s resultant displacement? 1. 40 m 2. 280 m 3. –280 m 4. 0 m •Remember: Displacement isn’t distance

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2.2 Velocity • The average speed of an object is defined as the total distance traveled divided by the total time elapsed – Speed is a scalar quantity • Speed and velocity
• Average speed totally ignores any variations in the object’s actual motion during the trip • The total distance and the total time are all that is important SI units are m/s

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Velocity • It takes time for an object to undergo a displacement • The average velocity is rate at which the displacement occurs • generally use a time interval, so let t i = 0
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## This note was uploaded on 01/02/2010 for the course PHY 101 taught by Professor Pralle during the Fall '08 term at SUNY Buffalo.

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PHY101_Chap2Fall09 - Chapter 2 2.1 Displacement Motion in...

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