Question

What is the magnetic force on a proton that is moving at 2.5 107 m/s to the left through a magnetic field that is 3.4 T and pointing toward you? The charge on a proton is 1.6 10-19 C. Use F = qv B sin(). **I know it's between C or D**
A. 4.0 10-12 N left
B. 4.0 10-12 N right
C. 1.4 10-11 N up
D. 1.4 10-11 N down

Answer 1

I have the answer, I just dont know how you're suppose to find out if it moves up or down

Answer 2

Use the left hand rule to determine the direction!

Answer 3

whats the left hand rule?

Answer 4

http://sciencecity.oupchina.com.hk/npaw/student/glossary/flemings_left_rule.htm

Answer 5

Be consistent in physics and use the right hand rule, especially since the formula you need to use requires as much. Here's the formula, Lorentz's Force Law:\[F=q(E+v \times B)\]where f is the force on the charged particle; E is the electric field; v is the particle's velocity; and B is the magnetic field. The "v × B" part is what uses the right hand rule. According to the right hand rule, you point the fingers of your right and in the direction of the particle's velocity. Then curl your fingers toward the direction of the magnetic field. Your thumb will then point in the direction of the force on the particle.

Alternately, you can point your index finger in the direction of the particle's velocity, and then point your middle finger in the direction of the magnetic field. Your thumb will then point in the direction of the force.

It's important to note one thing. If the particle had instead been an electron, it's charge, q, would be negative which would make the force act in the opposite direction than the force acting on the proton.