Find the coefficient of static friction between the rod and the rails. A rail gu

Question

Find the coefficient of static friction between the rod and the rails.

A rail gun uses electromagnetic forces to accelerate a projectile to very high velocities The basic mechanism of acceleration is relatively simple and can be illustrated in the following example. A metal rod of mass 20.0 g and electrical resistance 0500 1 rests on parallel horizontal rails that have negligible electric resistance. The rails are a distance L = 800 cm apart. (Figure 1) The rails are also connected to a voltage source providing a voltage of V = 500 V. The rod is placed in a vertical magnetic field. The rod begins to slide when the field reaches the value B = 0.123 T . Assume that the rod has a slightly flattened bottom so that it slides instead of rolling. Use 9.80 m/S^2 for the magnitude of the acceleration due to gravity.

Explanation / Answer

rail gun uses electromagnetic forces to accelerate a projectile to very high velocities.

Current I in the rod = V/R = 5/0.5 = 10 A
Length through which B crosses = 0.08 m
Magnetic field B = 0.123 T

Force acting on the rod = ILB = 10*0.08*0.123 = 0.0984 N

Frictional force = mg
Net force = 0.0984 - mg = 0 when motion just begins.

= 0.0984 / (0.02*9.8) = 0.502

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