Principles of Technology
Review:
Any or all of this could be on the final exam. Expect what you see!
Mechanical Force (1:1)
1. What is a force?
2. What are the SI and English units of force?
3. What happens when forces are unbalanced?
4. A torque wrench has a lever arm of 30 cm. A force of 450 newtons is applied at the end of the wrench. Calculate the
torque.
5. A torque wrench has a lever arm of 18 inches. A force of 85 pounds is applied at the end of the wrench. Calculate the
torque.
6. A torque of 1750 N·M is produced by a wrench with a lever arm of 75 cm. How much force is being applied?
Mechanical Work (2:1)
7. Barbara lifts a 180 lb. barbell to a height of 7.25 feet. How much work does she do?
8. While showing off for the guys, she holds the 180 lbs. over her head for 11.37 minutes. If you ignore the loss due to
inertia, how much work does she do while maintaining the barbell in the raised position?
9. How many radians are in a full circle?
10. A winch with a crank handle one foot long applies a torque of 35 lb·ft. How much work is done to turn the winch
through 15 revolutions?
11. A block and tackle is used to lift a load weighing 600 pounds. Robin lifts the load a distance of 1.25 feet by pulling on
the rope with a force of 200 pounds over a distance of 4 feet. Calculate the following:
11a. input work
11b. output work
11c. efficiency of the block and tackle
12. If a winch has a lever arm of 1.25 feet and requires 40 pounds to turn the crank, how much work is done to turn the
winch through 15 revolutions?
Fluid Force (1:2)
1. What is the Prime Mover in the Fluid System?
2. What are the 2 main types of fluids?
3. A volume of 350 cm3 of bean farts has a mass of 30 grams. Calculate the density of the resulting cloud of noxious
fumes.
4. The height of a water tank is 750 feet above a valve. If the weight density of water is 62.4 lbs/ft3 what is the pressure
at the valve?
5. A backhoe has a 4.75 in2 piston powered by a pump which produces 2250 lbs./in2 of hydraulic pressure. How much
force is being produced?
Fluid Work (2:2)
1. A pump needs 210,000 N·m of work to lift 51.3 m3 of fluid. What is the pressure difference?
2. What is the displacement of a hydraulic cylinder which completes 5540 ft·lb of work at a constant pressure of 11.3
lb/ft2?
3. A piston is displaced by a constant pressure of 150 N/m2. The cylinder moves a fluid volume of 0.025 m3 when the
piston moves 11 cm.
3a. Calculate the work required to move the piston 11 cm.
3b. Calculate the force on the piston if the piston face has an area of 0.035 m2.
4. A pressure of 2250 lb/in2 is applied to the face of a piston in a closed hydraulic cylinder, causing a total force of 666.67
lb. on the face of the piston. Calculate the following:
4a. The area of the piston face.
4b. The diameter of the piston.
4c. The volume of fluid displaced when the piston moves 10 inches.
4d. The fluid work done by the piston when moving the 10 inches.
Electrical Force (1:3)
1. What is the Prime Mover in the Electrical System?
2. What are the most common sources of AC and DC current?
3. What is moving in an electrical system?
4. Draw a schematic diagram of a simple circuit and label the 4 main components.
5. Draw a schematic diagram of a 12 volt DC circuit with 2 loads connected in series. Assuming no loss of voltage, label
what the voltages will be at each of the loads.
6. Draw a schematic diagram of a 6 volt DC circuit with 2 loads connected in parallel. Assuming no loss of voltage, label
what the voltages will be at each of the loads.
Electrical Work (2:3)
1. What is the basic unit of electrical charge?
2. How many electrons are in 1 unit of charge?
3. A dead 12 volt battery can store 12,000 coulombs of charge. How much electrical work is done to completely recharge
the battery?
4. A 12 volt battery does 650 volt coulombs of work. How much charge has it moved?
5. An electrical motor does 1500 N·m of mechanical work while it uses up 1850 joules of electrical energy. What is the
efficiency of the motor?
6. A 110 volt electric motor draws a current of 13 amps for 15 seconds. How many coulombs of charge are moved?
7. How much charge is moved by a motor if a current of 17.3 amps operates for 1l.5 minutes?
8. If the above motor operates at 220 volts, how much work is completed in the 11.5 min?
Thermal Force (1:4)
1. What is the Prime Mover in the Thermal System?
2. What causes heat?
3. Convert 57.6 deg. C to deg. F.
4. Convert 43 deg. F to deg. C.
5. Convert 12 deg. F to deg. C.
6. The temperature inside is 68 deg. F and outside it is 37 deg. C. What is delta-T ___________ , and will the heat move
from outside to inside or inside to outside (circle the answer)?