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標題:
發問:
In a 400M race, a runner first accelerates uniformly from rest to a speed of 8ms-1. He then maintains this speed and finishes the race in 52s. How long does the rinner take to reach the speen of 8ms-1.
最佳解答:
Let t be the time required to accelerate to 8 ms-1. So, Distance travelled by the uniform velocity 8 ms-1 = 8(52 - t) = (416 – 8t) m By the equation of motion, s = (u + v)t / 2 400 – (416 – 8t) = (0 + 8)t / 2 -32 + 16t = 8t t = 4 So, the time required is 4 s.
其他解答:
52-t=400/8 416-8t=400 t=2s 2007-10-16 22:06:02 補充： 52-t係加完速的時間400/8係黎至 8= 400/52-t speed = distance / time0D7DAC4E7B8CAAC5
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F.4 Mechanics發問:
In a 400M race, a runner first accelerates uniformly from rest to a speed of 8ms-1. He then maintains this speed and finishes the race in 52s. How long does the rinner take to reach the speen of 8ms-1.
最佳解答:
Let t be the time required to accelerate to 8 ms-1. So, Distance travelled by the uniform velocity 8 ms-1 = 8(52 - t) = (416 – 8t) m By the equation of motion, s = (u + v)t / 2 400 – (416 – 8t) = (0 + 8)t / 2 -32 + 16t = 8t t = 4 So, the time required is 4 s.
其他解答:
52-t=400/8 416-8t=400 t=2s 2007-10-16 22:06:02 補充： 52-t係加完速的時間400/8係黎至 8= 400/52-t speed = distance / time0D7DAC4E7B8CAAC5
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