magnetic fields question

[klm0101]

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I have a question about magnetic force. I know the equation is F=qvBsintheta, and that magnetic force do no work, so that means that there is no change in KE, so that means speed doesn't change. But I am getting confused, does that mean magnetic fields won't accelerate a particle too? Because don't magnetic fields cause centripetal force, which means there would be acceleration? So is it just that there is acceleration causing the velocity to change direction but not speed? sorry if this is confusing, i think i am just confusing myself even more.

 

[AZFutureDoc]

Speed stays the same, and yes acceleration is constantly changing. However, this does not mean kinetic energy does not change. It will stay the same unless there are other forces. Imagine it like this: At one instant, it is going one direction, say 5 m/s. The next instand, it is going another direction, but also at 5 m/s. So you change the direction of displacement, yes, but at all times, the kinetic energy is the same.