Ali and abdi go for a walk along an abandoned railroad truck , ali puts one ear next to a rail, while abdi 300m away taps in the rail with a stone . how much sooner does ali hear the sound (speed of sound in steel is 6500m/s).

The 20@kg wheel has a radius of gyration about its center g of kg = 300 mm. when it is subjected to a couple moment of m = 50 n # m, it rolls without slipping. determine the angular velocity of the wheel after its mass center g has traveled through a distance of sg = 20 m, starting from rest.

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?

The average density of the planet uranus is 1.27 103 kg/m3. the ratio of the mass of neptune to that of uranus is 1.19. the ratio of the radius of neptune to that of uranus is 0.969. find the average density of neptune.