The answer is that simply knowing the particle has an acceleration is not enough to tell you where the particle will be.

答案是这样的,仅仅知道质点的加速度,是不足以告诉你它接下来的运动的

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In other words, you don't have to be moving actually in a circle to have the acceleration.

也就是说,你不必真的在一个圆上运动以获得相应的加速度

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This particle is constantly changing its direction, but it therefore has an acceleration and the acceleration, we have shown here, is pointing towards the center.

这个质点恒定地改变它的运动方向,因此它具有加速度,而且这个加速度,我们前面也讲过了,指向圆心

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What's your plan for measuring acceleration if some little thing is moving?

如果某个小物体在运动,你要如何测量加速度

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That also cannot happen, so they're moving with the same acceleration.

这也不可能发生,所以它们以相同的加速度运动

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Even at=0, and it has an initial velocity, so even without any acceleration, it will be moving from y0 to y0+vt.

即使at=0,它仍然有初速度,因此即使加速度为0,它也会从y0运动到y0+vt

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When a particle moves in a circle, it has an acceleration towards the center of this size, v^2 over R.

当一个质点在圆周上运动时,它有一个指向圆心的加速度,v^2 / R

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It tells you when a particle moves in a circle, it has an acceleration in a negative R direction, namely directed towards the center.

它告诉你当一个物体在圆周上运动时,它有一个在 -R 方向的加速度,也就是说是直接指向圆心的

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Now, what happens if the elevator is accelerating upwards with an acceleration a?

现在如果电梯向上以加速度 a 运动,会发生什么呢

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We said, "Let's take, for the simplest case that we can possibly imagine, namely a particle moving in one dimension along the x-axis with a constant acceleration a.

我们说过,"考虑我们可以想象的最简单的情况,即质点在一维空间运动,沿着 x 轴且保持恒定加速度 a

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Whenever you see a particle moving in a circle, even if it's at a constant speed, it has an acceleration, v square over r directed towards the center.

只要看到质点做圆周运动,即使是匀速圆周运动,也存在一个加速度,大小为 v^2 / r,方向指向圆心

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So, this certainly describes a particle whose acceleration is a.

它确实描述了一个加速度为a的质点的运动

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