Mechanical Aptitude Flashcards

A lever is used to lift a 200-lb load. If the effort arm is 6 feet and the resistance arm is 2 feet, how much effort force is needed?

Answer: 67 lbs

Using the lever formula: Effort × Effort Arm = Load × Resistance Arm → Effort = 200 × 2 / 6 ≈ 67 lbs.

Which type of pulley system provides the greatest mechanical advantage?

Answer: A block and tackle with 4 rope segments

A block and tackle with 4 supporting rope segments provides a mechanical advantage of 4, reducing required effort to one-fourth of the load.

What happens to water pressure at the base of a standpipe as the height of water in the pipe increases?

Answer: Pressure increases

Water pressure increases with depth; every additional foot of water height adds approximately 0.434 psi to the base pressure.

A gear with 40 teeth meshes with a gear with 10 teeth. If the larger gear rotates at 100 RPM, how fast does the smaller gear rotate?

Answer: 400 RPM

Gear speed ratio is inverse to tooth count: 100 × (40/10) = 400 RPM for the smaller gear.

Which of the following best describes the function of a pressure relief valve?

Answer: It opens to release pressure when a set limit is exceeded

A pressure relief valve automatically opens to vent excess pressure, protecting the system from damage when pressure exceeds a preset threshold.

A firefighter uses a pry bar (a Class 1 lever) to open a door. If the fulcrum is placed very close to the door, what is the effect?

Answer: The effort required decreases significantly

Placing the fulcrum close to the load greatly increases the effort arm relative to the resistance arm, providing high mechanical advantage and reducing effort needed.

Two pipes carry water to a junction, then a single larger pipe carries it away. If the combined flow rate from the two input pipes equals 80 GPM, what must the output pipe carry?

Answer: 80 GPM

Conservation of mass requires the output flow to equal the combined input flow, so the output pipe must carry 80 GPM.