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.…
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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