Mechanical Aptitude Principles Flashcards

A gear train has a driver of 12 teeth meshed with a 36-tooth gear, which is on the same shaft as a 12-tooth gear driving another 36-tooth gear. What is the overall speed reduction?

Answer: 9 to 1

Each stage reduces speed 3:1, and two stages multiply to 9:1.

Friction between two surfaces generally does what to motion?

Answer: Opposes motion

Friction is a resistive force that always opposes the relative motion of surfaces.

Which arrangement gives a wrench the most turning power on a stubborn bolt?

Answer: A longer handle

A longer handle increases the lever arm, producing more torque for the same force.

Hot air rises primarily because it is what compared to cold air?

Answer: Less dense

Heated air expands and becomes less dense, so it rises above cooler, denser air.

A cam on a rotating shaft is typically used to do what?

Answer: Convert rotary motion into reciprocating (up-and-down) motion

A cam's irregular shape converts rotation into back-and-forth linear motion of a follower.

When you pump a bicycle tire, the air inside is compressed. What happens to the air pressure?

Answer: It increases

Compressing a gas into a smaller volume increases its pressure.

Two ropes support a hanging weight at equal angles. If the angle between them widens, the tension in each rope does what?

Answer: Increases

Wider support angles require greater tension in each rope to hold the same load.