A professional race-car driver buys a car that can accelerat

问题描述:

A professional race-car driver buys a car that can accelerate at +5.9m/s^2.The racer decides to race against another driver in a souped up stock-car.Both start from rest,but the stock-car driver leaves 1.0s before the driver of the race car.The stock car moves with a constant acceleration of +3.6m/s^2.
a.find the time it takes the race-car driver to overtake the stock-car driver.
b.Find the distance the two drivers travel before they are side by side.
c.find the velocities of both cars at the instant they are side by side.
1个回答 分类:英语 2014-09-23

问题解答:

我来补答
一个专业的赛车手,买了车,可以在+5.9米/秒^2加速.赛车手决定和另一个司机经改装的一辆车进行比赛.都开始休息,然后改变车司机离开提前1.0秒的赛车司机.改装车的加速度+3.6米/秒^2.
A.找到赛车手超过改装车所花费的时间.B.找到两位车手并排在一起时,距离出行地的距离.C.找到两辆车在即时他们并排的速度.他们是并排的瞬间.
A.设超车所用时间为t,超车时刻二车到达同一位置.
赛车手:x1=a1t^2/2=5.9t^2/2
改装车:x2=a2(t+1)^2/2=3.6*(t+1)/2
到达同一位置:x1=x2
5.9t^2/2=3.6*(t+1)/2
t=3.5s
B.x1=5.9*3.5^2/2=36.1m
C.赛车手车速v1=a1t=5.9*3.5=20.65m/s
改装车车速v2=a2t=3.6*(3.5+1)=16.2m/s
再问: A的答案是4.6s 不是3.5s. 我不知道怎么做的。而且比他提前1秒不是应该用更少的时间吗?为什么不是t-1?
再答: A改变车司机离开提前1.0秒。所以到相遇的时间应该是3.5+1=4.5s.小数点后面有误差。 赛车手用的时间是t=3.5s,改装车用的时间就是t+1. 当然,如果我们设改装车用时间为t,赛车手用的时间为是t-1了。
 
 
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