题目

英语翻译
A person is standing on a scale that is located on a platform at the surface of the earh.The platform is supported by a machine that can move the platform up and down at various accelerations while keeping it level.If the person's weight has apparently doubled according to the reading on the scale,what is the acceleration of the platform?
A.about 9.8 m/s^2 up
B.about 9.8 m/s^2 down
C.about 19.6 m/s^2 up
D.about 19.6 m/s^2 down
E.It cannot be determined without knowing the mass of the person.

提问时间：2021-04-06

答案

在地球表面的一个平台上有一台秤,秤上站着一人,平台由一机器支撑,可以上下做不同的水平加速运动.当台秤读数的是此人体重的两倍时,平台的加速度是多少?
A.约9.8m/s^2,向上
B.约9.8m/s^2,向下
C.约19.6m/s^2,向上
D.约19.6m/s^2,向下
E.不知道人的质量无法求解.
F(台秤给人的支撑力)-W(人的重力) = ma
Let F - W = mg
So,mg = ma,a = g (upward)
Ans :(A)