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Help please!!! A car stops in 120m. If it has an acceleration of -5m/s^2, how long did it take to stop?

Help please!!! A car stops in 120m. If it has an acceleration of -5m/s^2, how long-example-1
User Carl Zheng
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1 Answer

4 votes

Think about the reverse problem: a car is still, and it reaches its top speed in 120m, with the same acceleration (compare it to sending people inside a room until it's full, or bringing people outside until it's empty, with 5 people entering/leaving each second).

Your car moves according to
\Delta x = \frac12 a t^2, where
\Delta x is your 120 meters, and a is 5[tex]ms^{-2}[tex]. It's an equation in t, solve for it and take the positive root (why?)


User Codingrose
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