Mechanical Comprehension Study Guide for the ASVAB

General Information

• The Mechanical Comprehension section of the ASVAB measures aptitude in understanding basic mechanics.
• While not as widely used as other sections, it is crucial for specific military roles.

Principles of Mechanical Devices

• Topics covered: Mechanical advantage, simple machines, structural support, properties of materials.

Mass

• Mass is the amount of matter in an object, independent of gravity.

Force

• Forces are vector quantities with magnitude and direction.
• Types of forces include pushes, pulls, attraction, and repulsion.
• For an object with no acceleration (constant velocity), the sum of forces is zero.

Gravity

• Gravity is the attractive force between two masses, described by the gravitational force equation.
• It causes objects to fall to the ground due to Earth's pull.

Friction

• Friction opposes motion and results from microscopic interactions between surfaces.
• Energy in a frictional system includes potential, kinetic, and work done by friction.

Compression

• Compression is a force applied inward, squeezing an object.

Tension

• Tension is a pulling force measured in pounds or Newtons.

Newton's Laws of Motion

• First Law: Objects remain at rest or in uniform motion unless acted upon by an external force (law of inertia).
• Second Law: Acceleration is proportional to force and inversely proportional to mass.
• Third Law: Every action has an equal and opposite reaction.

Fluid Dynamics

• Relates to air pressure, water pressure, and tank filling/emptying.

Air Pressure

• Caused by gravity pulling air molecules, leading to greater pressure at Earth's surface.

Water Pressure

• Increases with depth due to the weight of water above.
• Hydraulic lifts use fluid pressure to lift heavy objects using incompressible fluids.

Filling and Emptying Tanks

• Involves converting flow rates and combining inflow/outflow to determine fluid volume over time.

Torque

• Torque is the twisting force on an object.

Work, Energy, and Power

• Scalar quantities important in physics.

Work

• Defined as force causing an object to move a distance.
• Measured in Joules (Newton meters).

Energy

• Capacity to perform work.
• Total mechanical energy: sum of potential and kinetic energy.
• Nonconservative forces add additional work to total energy.

Kinetic Energy

• Energy of motion, measured in Joules.
• Related to work via the work-energy theorem.

Potential Energy

• Energy of position, with various forms like gravitational potential energy.
• Conversion between potential and kinetic energy occurs during motion.

Other Types of Energy

• Chemical: Energy from molecular bonds.
• Electric: Energy from moving electrons (current).
• Nuclear: Energy from the atomic nucleus.
• Solar: Energy from the sun.

Power

• Amount of work done over time, measured in watts (joules per second).