Principles of Mechanical Devices

Principles of Mechanical Devices

• The ASVAB test section covers mechanical advantage, simple machines, compound machines, structural support, and properties of materials.

Mass

• Mass is the amount of matter in an object, independent of gravity.
• Matter is anything that has mass and takes up space.

Force

• Forces are interactions between two or more objects, possessing magnitude and direction.
• Forces can be thought of as "pushes" or "pulls" (e.g., attraction, repulsion, gravity, electric force).
• When an object experiences no acceleration (constant velocity), the sum of forces acting on it is zero.

Gravity

• Gravity is the force of attraction between two masses.
• Gravity is described by the equation: Fg = G * m1 * m2 / r^2.
• Gravity is only attractive and the reason objects fall towards the ground.

Friction

• Friction is the force opposing an object in motion, always opposite to the direction of motion.
• Friction arises from microscopic interactions between surfaces.
• In a system involving friction, total energy is found by summing potential energy, kinetic energy, and work done by friction.

Compression and Tension

• Compression is a force applied inward, squeezing an object.
• Tension is a force exerted when pulling, typically measured in pounds or Newtons.

Newton's Laws of Motion

First Law

• An object at rest will stay at rest, and an object in motion will stay in motion unless acted on by an outside force.
• This law is also referred to as the law of inertia.

Second Law

• The acceleration of an object is directly proportional to the force exerted, and inversely proportional to its mass.

Third Law

• For every action, there's an equal and opposite reaction.

Fluid Dynamics

• Questions typically relate to air pressure, water pressure, and filling/emptying tanks.

Air Pressure

• Air pressure is the weight of the atmosphere surrounding Earth, caused by the attractive force of gravity.
• Atmospheric pressure is greater at Earth's surface due to increased atmospheric density.

Quiz on mechanical advantage, simple machines, compound machines, structural support, and properties of materials from the ASVAB test.