if you had a sheet of copper in a strong permanent magnet, with the plane of the sheet perpendicular to the magnetic field, and quickly jerk it out,a. you will feel no magnetic forceb. any force you feel will be due mainly to iron impurities in the copper itself is not magneticc. you will experience a magnetic force opposing your action d. you will experience a magnetic force assisting your actione. none of these
C. It's called magnetic or eddy-current damping, and the force is proportional to the speed of plate movement, the conductivity of the copper, the square of the magnetic field strength and the volume of copper in the field. Basically you can think of the copper plate as a series of short-circuited coils which generate circulating currents which in turn generate magnetic fields opposing the motion, not unlike a shorted generator. Since the current increases as the conductivity of the plate does, it's especially noticeable with thick plates of copper and aluminum. (You don't want magnetic materials like iron because the magnetic force will interfere with isolating and feeling the damping force.) When damping force is proportional to velocity it's often called viscous damping, which is just how it feels, like the plate is immersed in honey.
