AR MG Mechanical Contractor Exam
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
Section 1: Mechanical Systems and Fundamentals
1. What is the primary function of a mechanical contractor when
installing a commercial HVAC system?
A. Design the building's structural foundation
B. Install, maintain, and repair mechanical equipment and associated
systems within the contractor's authorized scope
C. Perform all electrical utility distribution work
D. Inspect and certify all building fire-resistance assemblies
,Rationale: Mechanical contractors are responsible for installing,
maintaining, and repairing mechanical systems within their licensed
scope. These systems may include heating, ventilation, air
conditioning, refrigeration, piping, and related equipment. Structural
engineering, utility distribution, and fire-resistance inspections
generally fall under other professional or regulatory responsibilities.
2. Which type of energy does a rotating mechanical shaft primarily
transmit?
A. Chemical energy
B. Nuclear energy
C. Mechanical energy
D. Radiant energy
Rationale: A rotating shaft transmits mechanical energy in the form of
torque and rotational motion. This energy can drive fans, pumps,
compressors, and other equipment. Chemical energy is associated
with fuel reactions, while radiant energy is transmitted through
electromagnetic radiation.
3. What is the SI unit of pressure?
A. Joule
,B. Watt
C. Newton
D. Pascal
Rationale: The pascal (Pa) is the SI unit of pressure and is equal to one
newton per square meter. Mechanical contractors also commonly
encounter pounds per square inch (psi), inches of water column (in.
w.c.), and feet of water column when measuring system pressures.
4. A pump moves 120 gallons of water in 2 minutes. What is its
average flow rate?
A. 30 gallons per minute
B. 60 gallons per minute
C. 90 gallons per minute
D. 120 gallons per minute
Rationale: Flow rate is calculated by dividing the volume moved by
the time required. Therefore, 120 gallons ÷ 2 minutes = 60 gallons per
minute (GPM). Accurate flow calculations help contractors select
pumps, determine pipe sizes, and verify system performance.
5. Which instrument is commonly used to measure air velocity in an
HVAC duct?
, A. Megohmmeter
B. Torque wrench
C. Anemometer
D. Refrigerant recovery cylinder
Rationale: An anemometer measures air velocity and is used during
HVAC testing and balancing. When combined with duct dimensions,
velocity measurements can help determine airflow. A megohmmeter
tests electrical insulation, while a torque wrench measures applied
rotational force.
6. What is the primary purpose of a mechanical drawing's scale?
A. To identify the contractor's license classification
B. To determine the age of the building
C. To relate drawing dimensions to actual physical dimensions
D. To specify the equipment's electrical frequency
Rationale: A drawing scale establishes the relationship between
measurements on a drawing and actual dimensions in the field.
Contractors use scaled drawings to estimate distances, coordinate
installations, and plan equipment placement. Written dimensions
generally take precedence over measurements scaled from drawings.
Questions and Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf
Section 1: Mechanical Systems and Fundamentals
1. What is the primary function of a mechanical contractor when
installing a commercial HVAC system?
A. Design the building's structural foundation
B. Install, maintain, and repair mechanical equipment and associated
systems within the contractor's authorized scope
C. Perform all electrical utility distribution work
D. Inspect and certify all building fire-resistance assemblies
,Rationale: Mechanical contractors are responsible for installing,
maintaining, and repairing mechanical systems within their licensed
scope. These systems may include heating, ventilation, air
conditioning, refrigeration, piping, and related equipment. Structural
engineering, utility distribution, and fire-resistance inspections
generally fall under other professional or regulatory responsibilities.
2. Which type of energy does a rotating mechanical shaft primarily
transmit?
A. Chemical energy
B. Nuclear energy
C. Mechanical energy
D. Radiant energy
Rationale: A rotating shaft transmits mechanical energy in the form of
torque and rotational motion. This energy can drive fans, pumps,
compressors, and other equipment. Chemical energy is associated
with fuel reactions, while radiant energy is transmitted through
electromagnetic radiation.
3. What is the SI unit of pressure?
A. Joule
,B. Watt
C. Newton
D. Pascal
Rationale: The pascal (Pa) is the SI unit of pressure and is equal to one
newton per square meter. Mechanical contractors also commonly
encounter pounds per square inch (psi), inches of water column (in.
w.c.), and feet of water column when measuring system pressures.
4. A pump moves 120 gallons of water in 2 minutes. What is its
average flow rate?
A. 30 gallons per minute
B. 60 gallons per minute
C. 90 gallons per minute
D. 120 gallons per minute
Rationale: Flow rate is calculated by dividing the volume moved by
the time required. Therefore, 120 gallons ÷ 2 minutes = 60 gallons per
minute (GPM). Accurate flow calculations help contractors select
pumps, determine pipe sizes, and verify system performance.
5. Which instrument is commonly used to measure air velocity in an
HVAC duct?
, A. Megohmmeter
B. Torque wrench
C. Anemometer
D. Refrigerant recovery cylinder
Rationale: An anemometer measures air velocity and is used during
HVAC testing and balancing. When combined with duct dimensions,
velocity measurements can help determine airflow. A megohmmeter
tests electrical insulation, while a torque wrench measures applied
rotational force.
6. What is the primary purpose of a mechanical drawing's scale?
A. To identify the contractor's license classification
B. To determine the age of the building
C. To relate drawing dimensions to actual physical dimensions
D. To specify the equipment's electrical frequency
Rationale: A drawing scale establishes the relationship between
measurements on a drawing and actual dimensions in the field.
Contractors use scaled drawings to estimate distances, coordinate
installations, and plan equipment placement. Written dimensions
generally take precedence over measurements scaled from drawings.
