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But things which were at rest will move at a constant velocity, opposite of the velocity that you have relative to me.
这些静止的东西都在匀速运动,方向正好跟你相对我运动的速度方向相反
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You can ask me where it will be nine seconds from now, eight seconds from now, how fast will it be moving.
你们可以问我九秒后它的位置,或者八秒后,以及它的运动速度
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So, if we do this calculation for an electron, saying it moves at 10 to the 5 meters per second, then what we end up with for a wavelength is 7 times 10 to the -9 meters.
如果我们已知电子以，10的5次方每秒的速度运动，那么做一个计算,可以得知它的波长是,7乘以10的负9次方米。
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And they are in motion and moving at very, very high speed.
它们都在运动,以非常非常高的速度运动。
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The angle is increasing at a steady rate, so we know it's going at a steady speed.
转过的角度以恒定速率增加,所以我们知道它以一个恒定的速度运动
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What that means is, if you know the velocity of the given time and you know the initial velocity, you know what time it is.
这个方程的意义是,如果你知道某个给定时刻的速度,并且知道初速度,你就能知道运动的时间
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You see how long you are in the air and the whole time you are in the air, you are traveling horizontally at this speed.
你可以知道在空中停留的时间,当你在空中运动的时候,你一直以这个水平速度在运动
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I'm asking what's the tangential speed as it moves along the circle?
它在做圆周运动时,切向速度是多少
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Let it go a little more, that gives you the velocity later.
让它再运动一小段距离,那就能得到稍后的速度
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At this instant, the planet may be moving at that speed.
在这个时刻,行星可能在以这个速度运动
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So, the average velocity may not tell you the whole story.
平均速度可能无法描述整个运动过程
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The fact that you don't need a force for it to move forever at a given speed in a given direction, that's not obvious, because in daily life you don't see that.
对于物体不需要力的作用就能保持,确定的速度和方向持续运动这一事实,它并非显而易见,因为在日常生活中你看不到这种情况
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c We know it's very specific for light because in this equation is c, the speed of light. So any time you go to use this equation, if you're trying to use it for an electron, just ask yourself first, does an electron travel at the speed of light?
我们知道它只对光适用是因为在这个方程里有,光速，所以下次你们用这个方程前，如果你们要把它用到一个电子上，先问问你自己，电子的运动速度是光速吗？
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What it means is if you'd release a rock at that location one second before with a certain speed that we can calculate, it would've ended up here with precisely the position and velocity it had at the beginning of our experiment.
它的意义在于,若在该处以特定速度抛出一个物体,这个速度可通过计算得到,一秒之后,物体会运动至我们设定的起点,并且速度为我们设定的初速度
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When you have a velocity in the moving plane frame and you want to find the velocity on the ground, you should add to every object in the plane the velocity of the plane with respect to the ground.
当你在运动的飞机上运动,然后你想找到相对于地面的速度,你就应该给每个物体加上,飞机相对于地面的速度
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For example, if you started here and you did all this and you came back here, the average velocity would be zero, because you start and end at the same value of x, you get something; 0 divided by time will still be 0.
例如,如果你从这里开始运动,经过这个过程又回到这里,平均速度就是0,因为初态和末态的位移相同,你得到了什么呢,0除以时间还是0
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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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If it's going in a circle, you will say from now on, that it, indeed, has an acceleration, even though no one's stepping on the accelerator, of amount v^2 over R.
如果它在一个圆周上运动,你会说从现在起它其实有加速度,即使没有人去踩油门,加速度大小为 v^2 / R
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If you want to know how fast it's moving at a given time, if you want to know the velocity, I just take the derivative of this answer, which is 10-10t.
如果你想知道它在给定时刻的运动有多快,如果你想知道它的速度,我只要对这个式子求导,得到10-10t
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