A rail gun uses electromagnetic forces to accelerate aprojectile to very high velocities. The basic mechanism ofacceleration is relatively simple and can be illustrated in thefollowing example. A metal rod of mass 40.0 g and electricalresistance 0.200 Ωrests on parallel horizontal rails that havenegligible electric resistance. The rails are a distance L= 10.0 cm apart. (Figure 1) The rails are also connected to avoltage source providing a voltage of V = 5.00 V .
The rod is placed in a vertical magnetic field. The rod begins toslide when the field reaches the value B =7.84×10−2 T . Assume that the rod has a slightlyflattened bottom so that it slides instead of rolling. Use 9.80m/s2 for the magnitude of the acceleration due to gravity.
Find μs, the coefficient of static friction between therod and the rails.
