College Physics
posted by Jen on .
A young person with normal hearing can hear sounds ranging from 20 Hz to 20 kHz. How many octaves can such a person hear? (Recall that if two tones differ by an octave, the higher frequency is twice the lower frequency)

2^{x}*20 = 20,000
Solve for x = number of octaves. Check my thinking.
2^{10}*20 = 20,480 Hz
2^{9}*20 = 10,240 Hz 
This is my problem:
A proton is propelled east with a speed of 2.1e6 m/s to a region where there is a magnetic field of strength 5 T directed perpendicularly out of the paper. Calculate the radius of the resulting circular trajectory of the proton. A proton has a mass of 1.67e27 kg and a charge of 1.67e19 C.
So I am looking for the radius of the loop, right? The formula I have is torque=current*area*strength*sin theta
I need to know torque or the total are to find the radius, right? How do I do that?