# Help Zone

### Student Question

A particle P travels with constant speed in a circle of radius 2.3 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 = 8.5 s and t = 27.7 s.

What are the steps? I don't understand how to solve this problem.

Physique ## Explanations (1)

• Explanation from Alloprof  Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

Hey,

This does sound a bit complicated; let me give you a hand!

As I suppose the figure is a circle in which we see the radius illustrated, I would suggest you imagine a cartesian plan at the bottom of the radius in which the y-axis splits the circle into two equal parts.

Then, you could use the formula: v = 2πr/T where v= speed, r=radius, and T=time to complete a revolution.

Then, measuring all the angles in a counterclockwise manner, you could do a proportion for each time given in the question, and calculate the angle associated. For example : 10 seconds/ 34 seconds = 0,29 x 360 degrees = 105,88 degrees. Finally, using trigonometry you should be able to get the answer.

I hope that helps!

If there's anything else, you know how to reach us!

Émilie