A proton and electron,each travelling at the same speed,enter a region of uniform magnetic field.They experience A) forces in the same direction and having ratio F_p/F_e = m_e/m_p B) forces equal in magnitude,but opposite in direction C) forces opposite in direction and having ratio F_p/F_e = m_e/m_p D) the same force

Question

Quizplus · Accepted Answer

The force experienced by a charged particle moving in a magnetic field is given by F = qvBsinθ, where q is the charge of the particle, v is the velocity of the particle, B is the magnetic field, and θ is the angle between v and B. 
Since both the proton and electron have the same speed, their velocities are in the same direction. However, the proton has a positive charge while the electron has a negative charge. Therefore, the angle θ between their velocities and the magnetic field will be opposite in direction. This means that the sine of the angle will be opposite in sign for the two particles. 
As a result, the two particles experience forces that are equal in magnitude (since they have the same speed and are traveling through the same magnetic field), but opposite in direction (due to the opposite sign of the sine function).

A Proton and Electron,each Travelling at the Same Speed,enter a Region