Block A weighs 50 N and Block B weights 30 N. Once block B is set into downward motion, it descends 5 m at a constant speed. Calculate the coefficient of kinetic friction using the work-energy theorem.

Along wire carrying a 4.2 a current perpendicular to the xy-plane intersects the x-axis at x=−1.7cm. a second, parallel wire carrying a 3.0 a current intersects the x-axis at x=+1.7cm. part a at what point on the x-axis is the magnetic field zero if the two currents are in the same direction? express your answer to two significant figures and include the appropriate units.