Rail Gun A rail gun uses electromagnetic forces to accelerate a projectile to ve

Question

Rail Gun

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 30.0g and electrical resistance 0.400? rests on parallel horizontal rails that have negligible electric resistance. The rails are a distance L = 10.0cmapart. (Figure 1) The rails are also connected to a voltage source providing a voltage of V = 5.00V .
The rod is placed in a vertical magnetic field. The rod begins to slide when the field reaches the value B = 0.118T . Assume that the rod has a slightly flattened bottom so that it slides instead of rolling. Use 9.80m/s2 for the magnitude of the acceleration due to gravity

Part A)

Find ?s, the coefficient of static friction between the rod and the rails.

Give your answer numerically.

Explanation / Answer

Here , for field B = 0.118 T

Force on the rod is

F = BIL

Now, for magnetic force equal to friciton for just moving

us * m* g = BIL

us * 0.030 * 9.8 = 0.118 * (5/0.4) * 0.10

us = 0.052

the coefficient of static friction between the rod and the rails is 0.052

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