Mechanical Engineering HW
Homework Page HW-6
MEHW-18 A spring has a constant of k = 50 lb/ft. Calculate the work necessary to compress the spring 6 inches from its uncompressed position.
A. 300 ft-lb B. 25 ft-lb C. 6.25 ft-lb D. 1.25 ft-lb
MEHW-19 Steam enters an ideal turbine at 600 psia and a temperature of 600° F. If the steam exhausts to a condenser operating at 90° F, what is the enthalpy of the exhaust steam?
A. 839.3 BTU/lb B. 885.2 BTU/lb C. 924.3 BTU/lb D. 1042.7 BTU/lb
MEHW-20 Find the quality of the exhaust steam if the turbine in the previous problem was 90% efficient, rather than ideal.
A. 70% B. 75% C. 79% D. 90%
MEHW-21 Determine the total horizontal force of the water acting on the dam shown below. The dam is 10 feet long and the water is 8 feet deep.
A. 277 lb B. 499 lb C. 19,970 lb D. 39,940 lb
Homework Page HW-7
MEHW-22 a and a 6-inch diameter piston at point b. Find
the hydraulic pressure and the force F that can be lifted by the jack when a force P = 25 lbs is applied to the handle as shown.
A. 125 lb B. 250 lb C. 1125 lb D. 4000 lb
MEHW-23 A 1 kW heating coil is submerged in ½ gallon of 60° F water. What will be the final water temperature if the coil operates for 10 minutes and all its heat is transferred to the water?
A. 122° F B. 176° F C. 196° F D. 212° F Boiling
MEHW-24 The theoretical maximum efficiency of a cyclic heat engine:
A. depends on the amount of friction in the cycle B. depends on the working fluid used in the cycle C. depends on the maximum and minimum temperatures in the cycle D. is 100%
MEHW-25 A four cylinder, 4-stroke, internal combustion engine has a bore of 4 inches and a stroke of 3 inches. If the engine develops, 65 hp at 900 rpm, find the brake mean effective pressure.
A. 202 psi B. 251 psi C. 314 psi D. 379 psi
Homework Page HW-8
MEHW-26 4,000 cu ft/min of water is available for use in a hydroelectric turbine. If the vertical drop of the water is 20 feet, and it enters and leaves the turbine at the same velocity and temperature as it enters, how much would be produced by a 100% efficient turbine?
A. 14.5 hp B. 75.6 hp C. 121 hp D. 151 hp
MEHW-27 A 1 cubic foot block of an unknown material displaces ¾ cubic feet when it floats in a liquid, with a specific gravity of 0.92. How much does this block of unknown material weigh?
A. 43 lbs B. 56 lbs C. 69 lbs D. 92 lbs
MEHW-28 A pile driver, with a 1000 lb hammer, drops five feet each time it strikes. Find the velocity of the hammer just prior to striking the pile.
A. 15.2 ft/sec B. 17.9 ft./sec C. 21.3 ft/sec D. 24.7 ft/sec
MEHW-29 If the pile driver, in the previous problem, drives the pile 6 inches into the ground with each stroke of the hammer, find the average force acting on the pile.
A. 1,000 lbs B. 5,000 lbs C. 10,000 lbs D. 12,000 lbs