A particle P travels with constant speed in a circle of radius 7.3 m and completes one revolution in 34.0 s (see Figure). The particle passes through O at t = 0 s. What is the magnitude of the average velocity during the interval from t = 11.9 s and t = 16.9 s.

Question

A particle P travels with constant speed in a circle of radius 7.3 m and completes one revolution in 34.0 s (see Figure). The particle passes through O at t = 0 s. What is the magnitude of the average velocity during the interval from t = 11.9 s and t = 16.9 s. 
The answer here is 1.30 m/s

I need help with:
What is the magnitude of the instantaneous velocity at t = 11.9 s?

What is the magnitude of the instantaneous acceleration at t = 16.9 s?

Thanks.

bobpursley · Answer

The issue is really direction. Find anagular displacement at those times

theta=w*t=2PI/34 *t

then, calculate each theta (radians), and velocity will be perpendicular to that angle.
Angle for velocity=theta+PI/2

Acceleration will be at -theta, alwas inward. If you want velocity in cartesian corrdiantes, you have to do some conversion.