Aproton, traveling with a velocity of 3.7 × 106 m/s due east, experiences a magnetic force that has a maximum magnitude of 5.4 × 10-14 n and direction of due south. what are the magnitude and direction of the magnetic field causing the force? if the field is up, then enter a number greater than zero. if the field is down, then enter a number less than zero.

The magnetic force (Lorentz force) experienced by the proton in the magnetic field is given by

since , because the velocity v and the force F in this problem are perpendicular, and so also the angle  between the velocity and the magnetic field B should be .

Let's find the magnitude of the magnetic field; this is given by


To understand the direction, let's use the right-hand rule:
-index finger: velocity
- middle finger: magnetic field
- thumb: force

Since the velocity (index) points east and the force (thumb) points south, then the magnetic field (middle finger) points downwards. So we write:
B = -0.091 T

B, if it was a lower watt she could put it in for her normal time and not burn it