Section 2.5 Motion with Constant Acceleration

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Constant Acceleration Equations• First equation

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Constant Acceleration Equations

• Derivation of the second equation: Displacement as a function of time

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The displacement during a time interval is the area under the velocity-time graph

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Second Constant Acceleration Equation

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What is the equation for this graph?

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Text: p. 44

Third Constant Acceleration Equation

• Combining both equations gives us a relationship between displacement and velocity:

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For motion with constant acceleration:

– Velocity changes steadily:

– The position changes as the square of the time interval:

– The change in velocity in terms of displacement, not time:

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Example

As you drive in your car at 15 m/s you see a child’s ball roll into the street ahead of you. You hit the brakes and stop as quickly as you can. Your reaction time is 0.45 sec. Once you hit the brakes you come to rest in 1.5 s. How far does your car travel from the time you see the ball?

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As you drive in your car at 15 m/s you see a child’s ball roll into the street ahead of you. You hit the brakes and stop as quickly as you can. Your reaction time is .45sec. Once you hit the brakes you come to rest in 1.5 s. How far does your car travel from the time you see the ball? DRAW A PARTICLE MODEL AND A GRAPH TO REPRESENT THE MOTION

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SOLVE

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