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Show the steps very clearly and briefly explain. 1. The driver of a car moving at 30m/s sees a wonderful dog 120m ahead. It takes her 0.5s to think and react before stepping on the brake. The car decelerates at a rate of 5ms^-2 when the brakes are locked. Will the dog be knocked down? 更新: What is 0.5*30? What does it mean? 更新 2: Why v is = 0

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As follows: The thinking distance: 0.5 x 30 = 15m The braking distance: v2 – u2 = 2as 02 - 302 = 2 ( - 5 )( s ) s = 90m Total stopping distance: 90 + 15 = 105m < 120m So the dog will not be knocked down. 2007-09-25 17:39:27 補充： Reminder: stopping distance = thinking distance + braking distance First find the thinking distance by s = vt. As the car decelerates at a uniform rate, we can apply the equations of motions to calculate the braking distance. Add them up and you will arrvie at the answer. 2007-09-25 22:36:11 補充： Firstly, during the reaction time (0.5s), the car is moving at 30 m /s, so the driver has already covered a thinking distance of 0.5 x 30m = 15m.That comes 0.5 x 30. Secondly,the Q states that the driver decelerates until the brakes are locked, so it means the car comes to rest and hence v = 0.

其他解答:7638E748CCC65837
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