# physics

A driver of a car travelling along a straight road with a speed of 72k.m./hour . Observes a sign board which gives the speed limit 54k.m./h.the signboard is 70m ahead when the driver applies break . Calculate the acceleration the car which will cause the car to pass the signboard at started?

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1. 72t + 1/2 at^2 = 70
72 + at = 54

so, a = -16.2 m/s^2 applied for t=10/9 seconds

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posted by Steve
2. A car is travelling on a straight road which has a speed limit of 95.0 km/h. The driver can see that just ahead the speed limit changes to 50.0 km/h. If she is currently travelling at the speed limit and she accelerates with a magnitude of 3.00 m/s2, what distance does the car go while slowing down to the new speed limit?

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