Uniform Circular Motion: Why is the velocity changing?

[physicsbaig]

I encountered this question in a practice test for an upcoming exam. My first inkling was to answer with (C) because in uniform circular motion, the acceleration always points towards the center of the circle, but the actual answer was D. Do you think this question was just an issue of direction and not magnitude? I know that acceleration nor the velocity are changing in magnitude BUT are changing in direction, given an axis of reference. What do you think? Thanks for your help in advance!

 

[BvU]

Hello Baiq and welcome to PF. Use the template (although I agree it's not extremely useful here). Read the guidelines too.
What I think is that you have the right conceptual picture (*). I take it that velocity in this context is a vector quantity and then there is only one answer that is not blatantly wrong.

(*) but then your first inkling would have to be that both B) and C) are right...

And: "given an axis of reference" is not a condition: they change, period.

 

[physicsbaig]

Thank you! Velocity is a vector quantity. That is something I'll remember.

 

[BvU]

And acceleration is too !