Question

Very simple question -- will reward with medal.

Lets say you have one electric powered skateboard that can push you 10 KM/h.

If you were to stand on TWO electric powered skateboard, one under each foot, will you go 20 KM/h?

Just something I've always wondered.

Answer 1

I'm fairly certain that it would remain the same. I don't think velocities like that can add; only the maximum value is the speed that it would go.

Answer 2

Nope - you'd still only be moving at 10 km/h.

It's all about your frame of reference. Consider the relative velocities of everything. If you're standing still on one skateboard moving at 10 km/h (relative to the ground - its "ground speed"), you too are moving at 10 km/h. When you add another identical skateboard to stand on, the surface you're standing on is still only moving at 10 km/h, and therefore so are you. The skateboards are acting independent of one another and the speeds aren't additive.

Now, if you stacked the skateboards on top of one another, that's a different story. Say you turn on the bottom one so that it starts moving at 10 km/h. That skateboard's ground speed is 10 km/h, as is the inactive skateboard's and your ground speed. But now say you turn on that second skateboard while the first is going at 10 km/h. Relative to the first skateboard, you and the second skateboard are going 10 km/h. However, the first skateboard is ALREADY moving at 10 km/h, meaning your ground speed (and that of the second skateboard) is actually 20 km/h. In this case the velocities are additive.

Answer 3

You will stay moving at the same velocity 10KM/h ... the relative velocity between the two skateboards equals zero and at the same direction ... these two velocities can't be added