Ellen needs to move a heavy box across the floor and then place it on a shelf that is four feet above the floor. which use of machines would most likely require the least amount of force in order to get the box on the shelf? sliding the box up an inclined plane to the shelf rolling the box up an inclined plane on a cart sliding the box across the floor and then lifting it using a pulley rolling the box across the floor in a cart and then using a pulley

Aball is thrown upward in the air, and its height above the ground after t seconds is h ( t ) = 57 t − 16 t 2 feet. find the time t when the ball will be traveling upward at 14.25 feet per second.

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.

Gas cloud 1 is likely to form a star. gas cloud 2 is not. based on this information, match the given conditions with each cloud