a rod moves with a speed of 1.6m/s on a rails 30cm apart. the rod has a resistance of 2.5ohm and a magnetic field of 0.35T, and the resistance of the U-shaped conductor is 21.0ohm at a given instant. calculate the induced emf, current, and external force needed to keep the rod's velocity at a constant at that instant

Acarpenter is driving a 15.0-g steel nail into a board. his 1.00-kg hammer is moving at 8.50 m/s when it strikes the nail. half of the kinetic energy of the hammer is transformed into heat in the nail and does not flow out of the nail. what is the increase in temperature of the nail after the three blows that the carpenter needs to drive the nail in completely? the specific heat of steel is 448 j/kg ∙ k. a) 2.7 k b) 1.8 k c) 7.7 k d) 8.1 k e) 3.6 k