Find μs, 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 10.0 g and electrical resistance 0.100 Ω rests on parallel horizontal rails that have negligible electric resistance. The rails are a distance L = 6.00 cm apart. The rails are also connected to a voltage source providing a voltage of V = 5.00 V .

Answer 1

We can find the force on the conducting rail, due to the current and magnetic field.
This may help. http://hyperphysics.phy-astr.gsu.edu/hbase/magneti…
Only the magnetic field will be responsible for this force (not electric field).
So we have F = q*v x B, where Force, v and B are vectors. We can rewrite q*v as I*L, where I is electric current, and L is length.

Find the current = Voltage/resistance = (5 V) / (0.1 Ω) = 50 A. Change length to SI units of 0.06 m, then we have I*L = q*v = 3 Coulomb*m/s. Multiply this by the electric field 1.63 x 10^-2 Tesla and the force is 4.89 x 10^-2 Newtons. This is the force just enough to overcome the friction.

Static Friction = (Normal Force)(static coefficient). In our case, the Normal Force is the weight = (0.01 kg)(9.8 m/s^2) = 9.8 x 10^-2 Newtons. Divide these to get coefficient of static friction = 0.499

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