1. The velocity is a relative concept. We may be stationary with respect to plat- form's frame but we are moving with respect to a train's frame, leaving the platform. This question is about the velocity used in the expression for force on a charged particle in magnetic field, F = q( x B). A device produces a constant and uniform magnetic field along the z-axis. The device is nothing but a large flat sheet parallel to yz-plane having sur- face current in direction. A person, Alice, is sitting in the laboratory (ie, the Alice's and laboratory's frame are identical) and another person, Bob, is riding a bicycle with velocity 10f. Alice push a charge with velocity 10 to- wards the device. Since Bob is riding a bicycle, he sees that the charge is stationary and device is moving with velocity -10. All velocities are in m/sec. Charge Charge Magnetic Field Magnetic Field Alice's or Laboratory's frame of reference Bob's frame of reference (a) What is the force on the charge in Alice's or laboratory's frame of reference, (b) How do you evaluate force on the charge in Bob's frame of reference. How do you deal with forces due to the moving current sheet. (c) Do your evaluation show the same force in (a) and (b) in non-relativistic limit? Note that the laws of physics remains same in all inertial frames. If you get different forces, please revisit your solution.