SOLUTION In this example, we will calculate the force on a proton moving in SET UP We use the right-hand rule to find the direction of the force. The force acts along the y axis, so we curl the fingers of our right hand around this axis in the a magnetic field. In (Figure 1), a beam of protons moves through direction from v toward B. We find that the force acts in the - y direction. a uniform magnetic field with magnitude 2.0 T, directed along the positive z axis. The protons have a velocity of magnitude SOLVE To find the magnitude of the force, use the equation of magnetic force on a moving charge. 3.0x105 m/s in the -z plane at an angle of 30 to the positive z axis. Find the force on a proton. The charge of the proton is F = qu B sin o q = +1.6 x 10-19 C. = (1.6 x 10-19 C) (3.0 x 105 m/s) (2.0 T) (sin 30 ) = 4.8 x 10-14 N. REFLECT We could also obtain this result by finding BJ and applying F = |q vBJ . However, since we were given the angle , the equation we used is more convenient. To check for consistency of units, we recall that 1 T = 1 N/(A . m). Part A - Practice Problem: An electron beam moves through a uniform magnetic field with magnitude 2.8 T, directed in the -z direction. The electrons have a velocity of 2.7x104 m/s in the y-z plane at an angle of 36 from the - z axis toward the +y axis. Find the force on an electron. Figure 1 of 1 Express your answer with the appropriate units. Your answer should be positive if the force is in the +x direction and negative if the force is in the -x direction. HA ? Value Units B 30 Submit Request