FCTC Mechanical Reasoning Principles 5 — Questions and Answers
Question 1: 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:
- Increase the mechanical advantage
- Decrease the force required
- Reduce the mechanical advantage (Correct answer)
- Have no effect on the force needed
Correct answer: Reduce the mechanical advantage
Applying force closer to the fulcrum (hinge) reduces mechanical advantage, requiring more force to open the door.
Question 2: Two identical pumps are connected in series. Compared to a single pump, the combination will:
- Double the flow rate
- Double the pressure output (Correct answer)
- Double both flow and pressure
- Halve the flow rate
Correct answer: Double the pressure output
Pumps in series add their pressure outputs while maintaining the same flow rate as a single pump.
Question 3: A fire hose nozzle is narrowed to increase water velocity. This is an application of:
- Boyle's Law
- Pascal's Principle
- The Venturi effect / continuity equation (Correct answer)
- Archimedes' Principle
Correct answer: The Venturi effect / continuity equation
The continuity equation states that reducing cross-sectional area increases fluid velocity to maintain constant flow rate.
Question 4: A ladder truck extends its aerial ladder while the vehicle is parked on a slight side slope. The greatest risk is:
- The ladder extending too slowly
- The vehicle tipping due to shifted center of gravity (Correct answer)
- The hydraulic fluid overheating
- The ladder sections binding together
Correct 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.
Question 5: Which type of valve is BEST suited for precise throttling of water flow in a fire suppression system?
- Gate valve
- Globe valve (Correct answer)
- Ball valve
- Check valve
Correct answer: Globe valve
Globe valves are designed for throttling because their internal disc can be partially opened to regulate flow with precision.
Question 6: A gear with 40 teeth drives a gear with 10 teeth. The driven gear rotates:
- At one-quarter the speed of the drive gear
- At the same speed as the drive gear
- Four times faster than the drive gear (Correct answer)
- Twice as fast as the drive gear
Correct 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.
Question 7: When a firefighter climbs a ground ladder that is leaning against a wall, the ladder's base tends to:
- Push into the wall
- Slide away from the wall (Correct answer)
- Lift off the ground
- Rotate clockwise
Correct 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.
FCTC Mechanical Reasoning Principles 5
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: