Question

急~!求高手解答这条英文的数学题~!!

3)An automobile starts from rest and accelerates to a final velocity in two stages along a straight road. Each stage occupies the same amount of time. In stage1, the magnitude of the car's acceleration is 3.0m/s^2. The magnitude of the car's velocity at the end of stage2 is 2.5 times greater than it is at the end of stage 1. Find the magnitude of the acceleration in stage 2.

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Answer 1

一部汽车从静止开始分两阶段沿一条直路开始加速到一个最终速度。每阶段占相同时间。第一阶段, 汽车的加速度的大小是3.0m/s^2。第二阶段末时汽车的速度是第一阶段末时的2.5倍。求第二阶段时汽车的加速度的大小。

解:
第一阶段末的速度v1 = a1*t = 3.0t
第二阶段末的速度v2 = v1 + a2*t = 2.5*v1 = 7.5t
所以 3.0t + a2*t = 7.5t
a2 = 4.5 (m/s^2)
因此第二阶段时汽车的加速度是4.5m/s^2。