WEBVTT

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Here is the problem: An object starts at 15 m/s and accelerates at negative 2.5 m/s squared for 4 s. How far does it go and how fast is it moving?

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Find displacement s and final velocity v for motion in a straight line with constant acceleration.

3
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List the known quantities. Unknown: displacement s and final velocity v.

4
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Final velocity.

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Displacement.

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So the answer is s equals 40 m, v equals 5 m/s.

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With constant acceleration, any three of displacement, initial velocity, final velocity, acceleration and time fix the other two. Each pair of unknowns is solved with the equation that does not contain the other unknown.

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Check v squared equals u squared plus 2as: 25 equals 25.