You and a friend sit still on a spinning merry-go-round. The merry-go-round spins 5 times every second, and to a stationary observer you have a speed of 9 m/s. From your frame of reference, what is the speed of your friend?

Question

Vocaloid · Answer

Well since they're both sitting still on the same object I would intuitively guess that it's 0 m/s

doesn't hurt to get a second opinion @sillybilly123

zarkam21 · Answer

@Shadow

Shadow · Answer

I would agree with @Vocaloid . Just imagine that you are in a car going at 35m/s. Look at a fellow passenger, and how fast to they appear to be moving?

You're right. Not at all ._.

zarkam21 · Answer

Thank you both!

sillybilly123 · Answer

depends how they're sitting

if A is sitting on  B's lap then they're in the same rest frame

but if A say sat opposite B on the edges of the thing, moving wrt the earth (E) but in different direction, have a look at their instantaneous velocity vectors:

$\mathbf v_{A|B} = \mathbf v_{A|E} - \mathbf v_{B|E} \ \ne \mathbf 0$

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