Uniform circular motion of a particle

[southernbelle]

Homework Statement

A particle is moving at a constant speed around a circle of radius 1.5 meters, and it completes 4 revolutions in 6 seconds.
a) What is its speed?
b) What is its radial acceleration?
c) In which direction does ar point?
d) What is it tangential acceleration, at?

Homework Equations

ac=v²/r
T=2pie times r/v
at= derivative of v/t
ar = -v²/r
ac = ar + at

The Attempt at a Solution

a.
6=8(pie)(1.5)/v
answer: 2pie
v=6.28 m/s

b.
ar = -v²/r
ar = 39.43/1.5
ar = 26.29 m/s²

c. I am not sure how to get the direction.

d. ac= ar + at
26.29 = 26.29 + at
at = 0?

 

[S[e^x]=f(u)^n]

think about what would happen if it accelerated constantly tangentially, and describe that motion, and see if it fits with your problem