Unit B — Systems in Action Unit Support

Line Master
B-5

Name:
Mechanical Advantage
Part A
1. List three examples of machines with a mechanical advantage > 1.

(a)

(b)

(c)

2. List three examples of machines with a mechanical advantage < 1.

(a)

(b)

(c)

3. Give an example of a machine with a mechanical advantage = 1.

Apackage of supplies is dropped from a plane, and one second later a second package is dropped. neglecting air resistance, the relative velocity of the 1st package viewed from the second will 56) a) increase. b) be constant. c) be zero. d) depend upon their weight. e) decrease

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.

Simple machines can a. increase force only b. decrease force only c. increase or decrease force