Question

A proton has a charge of 1.6 × 10-19 C and a mass of 1.67 × 10-27 kg. A proton moves with velocity 1.8 × 105 m/s in the z-direction. A magnetic field with B = 2.1 × 10-1 T points in the y-direction. Find the magnitude and direction of the magnetic force on the proton.
What is the angle between the proton’s velocity and the magnetic field?
45°
90°
180°
50°

I'll report you if you don't actually help. I'd like an actual explanation, please.

Answer 1

Hey

So first we need to know what the direction of the force is, using your right hand rule point your right hand in the direction of the velocity. You're saying its the z direction, not telling me whether it's into the page or out? Since its a positive z im assuming its coming out. The magnetic field is pushing it upwards, so the force is going in the negative x direction.

The force of a magnetic field is

F = Qv X B

What's weird is that you don't need mass in this equation. Actually you don't even need the formula, its telling you that they're all going in perpendicar directions. the answer is 90 degrees.

Now if you want to know the F just multiply the charge, velocity and magnetic field .

F = GVB

F = 6.048 E -15

Answer : 90 degrees, sin(90) = 1