Mechanical Reasoning Principles Flashcards

A firefighter must force open a door using a halligan bar. Placing the tool closer to the door's hinges rather than the latch will:

Answer: Reduce the mechanical advantage

Applying force closer to the fulcrum (hinge) reduces mechanical advantage, requiring more force to open the door.

Two identical pumps are connected in series. Compared to a single pump, the combination will:

Answer: Double the pressure output

Pumps in series add their pressure outputs while maintaining the same flow rate as a single pump.

A fire hose nozzle is narrowed to increase water velocity. This is an application of:

Answer: The Venturi effect / continuity equation

The continuity equation states that reducing cross-sectional area increases fluid velocity to maintain constant flow rate.

A ladder truck extends its aerial ladder while the vehicle is parked on a slight side slope. The greatest risk is:

Answer: The vehicle tipping due to shifted center of gravity

Extending a heavy aerial ladder shifts the vehicle's center of gravity, and a side slope increases the risk of tipping.

Which type of valve is BEST suited for precise throttling of water flow in a fire suppression system?

Answer: Globe valve

Globe valves are designed for throttling because their internal disc can be partially opened to regulate flow with precision.

A gear with 40 teeth drives a gear with 10 teeth. The driven gear rotates:

Answer: Four times faster than the drive gear

The gear ratio is 40:10 = 4:1, so the smaller driven gear spins four times faster than the larger drive gear.

When a firefighter climbs a ground ladder that is leaning against a wall, the ladder's base tends to:

Answer: Slide away from the wall

The firefighter's weight creates a horizontal force component at the base that pushes it away from the wall, so footings or heel placement are critical.