Tangential and radial acceleration of particle

[DG1102]

Homework Statement

In the case of a speeding particle undergoing circular motion:

a) the tangential acceleration is int he direction of the velocity vector and the radial acceleration points in the direction of the position vector
b)the tangential acceleration is perpendicular to the velocity vector and the radial acceleration points perpendicular to the position vector
c)the tangental acceleration is opposite the velocity vector and the radial acceleration points opposite the position vector
d)the tangential acceleration is int he direction of the velocity vector and the radial acceleration poitns opposite the position vector.

The Attempt at a Solution

I think the answer is either a or d, I'm not sure which way the radial acceleration points in this case.

 

[gabbagabbahey]

The position vector points from the origin (presumably the center of the circle in this case) outward to the particle. So, ask yourself what the motion of the particle would be if it had a tangential velocity and was (a) accelerating outward and (d) accelerating inward ...circular motion is only possible in one of these two cases.