標題:

Motion

發問:

A sports car accelerates along a straight line from rest at a rate of 6 ms^ -2 for 4s and then its acceleration changes to -4ms^ -2 for 2s.(a)Find the maximum speed of the car. Express the answer in km h^-1.(b)Find the final speed of the car. Express the answer in km h^-1.(c)Find the average acceleration of the... 顯示更多 A sports car accelerates along a straight line from rest at a rate of 6 ms^ -2 for 4s and then its acceleration changes to -4ms^ -2 for 2s. (a)Find the maximum speed of the car. Express the answer in km h^-1. (b)Find the final speed of the car. Express the answer in km h^-1. (c)Find the average acceleration of the car.Express the answer in ms^-2. 更新: answer: (a)86.4km h^-1 (b)57.6km h^-1 (c)2.67ms^-1

最佳解答:

(a)Find the maximum speed of the car. Express the answer in km h^-1. v = u + at = 0 + 6X4 = 24 m/s = 24X3600 = 86400 m / hr = 86.4 km / h (b)Find the final speed of the car. Express the answer in km h^-1. v = u + at = 24 + (-4)(2) = 16 m/s = 16X3600 = 57600 m/h = 57.6 km/h (c)Find the average acceleration of the car.Express the answer in ms^-2. Actually, I don't know what is "average acceleration" . I do it like this. ( 6X4 + (-4)X2 ) / ( 4 + 2 ) = 2.667 ms^-2

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