Some circular region with radius = 12 km centered at the equator. the air within this circular region is initially motionless with respect to the earth. the circular region is moved to the north pole along an isobaric surface in order to preserve its area. find the mean tangential velocity at this radius at the north pole.

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