Abeam of protons moves at 3.0 x 105 m/s through a uniform magnetic field with a magnitude of 2.0 t that is directed along the positive z-axis. the velocity of each proton lies in the x-z plane at an angle of 30 degrees to the +z-axis. find the force on the proton.

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.

Velocity is the speed of an object in a certain direction so you'd need to know speed and direction

Answer sample (c); // would be best because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest;