Basic hydraulics physics:

Energy:

1. If a circuit requires a flow of 5 gpm at 1000 psi, what is the theoretical horse
power required?
a. 5000 hp
b. 5 hp
c. 2.92 hp
d. 29.2 hp
Answer: c

2. Wasted energy in a hydraulic system ………. .

a. Makes the system more efficient
b. Is destroyed
c. Is converted to heat
d. Is used to do work
Answer: c

3. If a 500 pound weight is moved 2 feet, 1,000 foot-pounds of work has been
accomplished.
a. True
b. False
Answer: a

4. Power is defined as the rate of doing work.

a. True
b. False
Answer: a
Flow:

1. For an actuator to move in a hydraulic system there must be …….. .

a. Flow
b. At least 50 psi
c. At least 100 psi
d. Resistance
Answer: a

2. Changing the flow rate to an actuator will have no effect on the actuator
speed.
a. True
b. False
Answer: b

3. A certain tube has an inside diameter of 0.277 in. if the operating pressure is
3250 psig and the fluid velocity is 10 feet per second, what is the flow in
gpm through the given tube?
a. 0.032 gpm
b. 1.53 gpm
c. 0.024 gpm
d. 1.87 gpm
Answer: d

4. The rate of flow in gpm will determine actuator ……… .

a. Load
b. Pressure
c. Temperature
d. Speed
Answer: d
Pressure:

1. Increasing the load on an actuator will cause a decrease in system pressure.

a. True
b. False
Answer: b

2. Basic hydraulic physics is based on ……. .

a. Pascal’s law
b. Newton’s law
c. Bernoulli’s equation
d. The conservation of energy
Answer: a

3. If a force of 1000 lbs is applied over an area of 20 square inches what is the
pressure?
a. 5 psi
b. 10 psi
c. 50 psi
d. 100 psi
Answer: c

4. Pressure is a result of flow.

a. True
b. False
Answer: b

5. Pressure drop in a fluid conductor is due to leakage

a. True
b. False
Answer: b

6. Pressure is measured in in/lb

a. True
b. False
Answer: b
7. Resistance to flow in a hydraulic system creates …… .
a. Reduced speed
b. Pressure
c. Pump cavitation
d. Reduced actuator force
Answer: b

8. Pressure drop in a system is a result of ………..

a. Elbows
b. Reducers
c. Pipe length
d. All of the above
Answer: d

9. Pressure is a result of flow.

a. True
b. False
Answer: b
Fluids:

1. Viscosity is affected by the diameter of the fluid conductor.

a. True
b. False
Answer: b

2. If 50 gpm were flowing through a 2 square-inch pipe, the velocity of the

fluid would be ……. .
a. 8.02 ft/sec
b. 80.2 ft/sec
c. 10.21 ft/sec
d. 1.21 ft/sec
Answer: a

3. At a given flow rate, to increase the diameter of the fluid conductor would
cause the fluids velocity to increase.
a. True
b. False
Answer: b

4. If a cylinder is replaced with a larger diameter cylinder, the speed at which

the new cylinder extends and retracts will …….. .
a. Not change
b. Increase
c. Decrease
Answer: c

5. If the temperature of a hydraulic fluid increase the viscosity increases.

a. True
b. False
Answer: b
6. In this schematic, a pump runs at a rate of 20 gpm. If the system produces
1700 psi, what is the area of the piston (in square inches) required to extend
a 1000 lb weight a distance of 2 feet?

a. 0.85 square inches

b. 0.588 square inches
c. 19.836 square inches
d. 9.918 square inches
Answer: b
 Pumps:

Gear pump:

1. A gear pump is best suited for

a. Controlling pressure in a system
b. Changing flow in a system
c. Controlling pressure and changing flow
d. None of the above
Answer: d

2. Gear pumps ………… .

a. May be variable
b. Are usually not used in hydraulics
c. Change displacement with changes in rpm
d. Give constant output with constant rpm
Answer: d

3. If the speed of a gear pump is increases, ………. .

a. The pressure increases
b. The flow increases
c. Both flow and pressure increase
d. None of the above
Answer: b

4. Gear pump displacement increases with increased input rpm

a. True
b. False
Answer: b
5. All pumps …….
a. Have case drains
b. Have leakage
c. Control pressure
d. Are pressure compensated
Answer: b

6. Gear pumps ……… .

a. Trap fluid between the teeth and the housing
b. Have many moving parts
c. Are used to control pressure control valves
Answer: a

7. The two energy triangles of this pump indicate that ……..

a. The pump is bi-directional
b. The pump has twice the flow
c. The pump can be used as a motor
d. This type of pump does not exit
Answer: a

8. If the rpm of a gear pump does not change, then …………..

a. The system pressure will stay constant.
b. The flow will stay constant.
c. The flow will change according to cylinder load.
d. The pump will wear out sooner.
Answer: b
Vane pump:

1. A balanced vane pump uses an elliptical cam ring for opposing pressure
quadrants
a. True
b. False
Answer: a

2. Which of the following is not part of a vane pump?

a. Vane
b. Rotor
c. Cam ring
d. Barrel
Answer: d

3. Vane pumps ……………..

a. May be balanced or unbalanced
b. Are not positive displacement
c. Use a rotor for pumping
Answer: a

4. The difference between the balance and unbalanced vane pump is that in a
balanced v ane pump, ……….. .
a. The vanes are shaped elliptically
b. The drive shaft is shaped elliptically
c. The cam ring is shaped elliptically
d. The vanes are spaced unevenly
Answer: c

5. What keeps the vanes extended in a vane pump?

a. An internal spring
b. Back pressure
c. Centrifugal force
d. Return pressure
Answer: c
Piston pump:

1. Axial piston pumps …… .

a. Increase flow by increasing the swashplate angle
b. Decrease flow by increasing the swashplate
c. Are at full displacement when the rotating group is turning
Answer: a

2. Axial piston pumps utilize a rotating swashplate.

a. True
b. False
Answer: b

3. How is displacement changed in a piston type pump?

a. Change the angle of the swashplate
b. It cannot be changed
c. Change the pressure relief setting
d. None of the above
Answer: a

4. Increasing the angle of the swashplate in a piston pump …… .

a. Increase the pistons’ displacement
b. Allows the pump to rotate faster
c. Increase the pump’s outlet pressure
Answer: a
Fixed vs. variable:

1. Variable displacement piston pumps change the output flow by ……… .

a. Changing the pump’s rpm and/or swashplate angle
b. Changing only the swashplate angle
c. Changing only the pump’s rpm
d. None of the above
Answer: a

2. The arrow through this pump symbol indicates that …….

a. It is a pressure-compensated pump
b. It is a variable displacement pump
c. This type of pump does not exist
d. The pump needs to be replaced
Answer: b

3. The flow rate in a fixed pump depends on the rpm of the prime mover.
a. True
b. False
Answer: a

4. Which type of pumps can have variable displacement?

a. Vane pumps
b. Gear pumps
c. Piston pumps
d. Both vane and piston pumps
Answer: d
Pressure compensated:

1. When a pressure compensated pump is on stroke, the system is rated at flow

and working pressure.
a. True
b. False
Answer: a

2. A pressure compensated axial pump will de-stroke when flow is blocked.

a. True
b. False
Answer: a

3. Which type(s) of pumps can be pressure-compensated?

a. Vane pumps
b. Gear pumps
c. Piston pumps
d. Both vane and piston pumps.
Answer: d

4. When an axial piston pump is de-stroked or fully compensating, ……. .

a. The swashplate is at a 19-degree angle
b. The swashplate is at a 0-degree angle
c. There is no pressure
d. There is a maximum flow
Answer: b
 Actuators:

1. Hydraulic motors are best used for ………

a. Rotary motion
b. Linear motion
c. Both linear and rotary motion
d. Pumping fluid
Answer: a

2. Hydraulic motors are only built in two styles: vane and piston.
a. True
b. False
Answer: b

3. An actuator is used to convert hydraulic energy to mechanical energy.

a. True
b. False
Answer: a

4. There are three basic types of cylinders: ram, single acting and double
acting.
a. True
b. False
Answer: a

5. Cylinders can be used to ……. .

a. Push or pull a load
b. Tilt a load
c. Press
d. All of the above
Answer: d
6. Hydraulic motors are rated according to ………. .
a. Displacement only
b. Torque only
c. Displacement and torque
d. There is no rating
Answer: c

7. This energy triangle symbol indicates a ……. .

a. Hydraulic motor
b. Hydraulic pump
c. Hydraulic pump/motor
d. None of the above
Answer: a

8. At a constant pressure, a cylinder will produce more force on extend that on

retract.
a. True
b. False
Answer: a

9. How much force can a cylinder achieve if the effective area of a piston is 5
in2 with a pressure of 2,000 psi?
a. 4,000 lbs
b. 10,000 lbs
c. 100,000 lbs
d. 400 lbs
Answer: b
10.In the schematic shown here, the hydraulic motor is running at 2500 psi with
a flow of 30 gpm. If the motor is rotating at a speed of 980 rpm, what is the
output torque of the motor?
a. 5420-inch
pounds
b. 11943-inch
pounds
c. 76.5-inch
pounds
d. 2814-inch
pounds
Answer: d

11.Hydraulic motors are rated according to fluid displacement and torque

output.
a. True
b. False
Answer: a

12.Cylinders convert hydraulic power into ………. .

a. Rotary motion
b. Heat
c. Linear motion
d. Torque
Answer: c