[SOLVED] Force dealing with vectors 1. The problem statement, all variables and given/known data A uniform magnetic field of magnitude 1.47 T acts in the positive z direction. Find the magnitude of the force exerted by the field on a proton if the proton's velocity is <3Mm/s i + 3Mm/s j>. Answer in pN 2. Relevant equations [tex]F=QV \times B[/tex] 3. The attempt at a solution Being a cross product, I thought that it would just take the sin of the velocity vector. Since it is going at the same speed in x and y, the angle I calculated was 45, so it is 135 from the direction of the field. So after doing all that calculation, I get .7056. Where am I doing this wrong?