An electromagnetic rail gun can fire a projectile using a magnetic field and an electric current. Consider two conducting rails that are 0.500 m apart with a 50.0-g conducting projectile that slides along the two rails. A magnetic field of 0.750 T is directed perpendicular to the plane of the rails and points upward. A constant current of 2.00 A passes through the projectile.
(a) What direction is the force on the projectile?
(b) If the coefficient of kinetic friction between the rails and the projectile is 0.350, how fast is the projectile moving after it has traveled 8.00 m down the rails?
(c) As the projectile slides down the rails, does the applied emf have to increase, decrease, or stay the same to maintain a constant current?

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B