Aspring 1.50 m long with force constant 448 n/m is hung from the ceiling of an elevator, and a block of mass 10.9 kg is attached to the bottom of the spring.
(a) by how much is the spring stretched when the block is slowly lowered to its equilibrium point? (enter the magnitude only.) m
(b) if the elevator subsequently accelerates upward at 1.89 m/s², what is the position of the block, taking the equilibrium position found in part (a) as y = 0 and upwards as the positive y-direction. (indicate the direction with the sign of your answer.) m
(c) if the elevator cable snaps during the acceleration, describe the subsequent motion of the block relative to the freely falling elevator. what is the amplitude of its motion?

As part of an industrial process, air as an ideal gas at 10 bar, 400k expands at steady state through a valve to a pressure of 4 bar. the mass flow rate of air is 0.5 kg/s. the air then passes through a heat exchanger where it is cooled to a temperature of 295k with negligible change in pressure. the valve can be modeled as a throttling process, and kinetic and potential energy effects can be neglected. (a) for a control volume enclosing the valve and heat exchanger and enough of the local surroundings that the heat transfer occurs at the ambient temperature of 295 k, determine the rate of entropy production, in kw/k. (b) if the expansion valve were replaced by an adiabatic turbine operating isentropically, what would be the entropy production? compare the results of parts (a) and (b) and discuss.

More solar radiation is absorbed by earth’s surface than by

Why is rain likely when warm, moisture-laden air meets cold air? a) the lighter warm air will rise and cool down, causing condensation and rain. b) the cold air moves faster and pushes the warm air away, causing condensation and rain. c) the moisture in the warm air condenses on contact with the cold air, causing rain to fall. d) the cold air mixes with the warm air, reducing its temperature causing moisture to condense.