Mechanical Reasoning Principles Flashcards

Two identical cylinders contain gas at the same pressure. Cylinder A is kept at room temperature; Cylinder B is heated. Which cylinder has higher gas pressure after heating?

Answer: Cylinder B

At constant volume, gas pressure is directly proportional to absolute temperature (Gay-Lussac's Law), so the heated cylinder has higher pressure.

A motor drives a pump through a flexible coupling. The flexible coupling's primary purpose is to:

Answer: Compensate for minor shaft misalignment and absorb shock loads

Flexible couplings accommodate small angular or parallel misalignments and dampen vibration and shock between connected shafts.

A ball rolls down a frictionless ramp and then along a flat surface. On the flat surface, the ball will:

Answer: Continue at constant speed indefinitely

On a frictionless flat surface there is no net horizontal force, so Newton's first law dictates the ball continues at constant velocity.

A torque wrench is set to 80 ft-lb. The technician applies force 2 feet from the bolt center. How much force must be applied?

Answer: 40 lb

Torque = force × distance; 80 ft-lb = F × 2 ft, so F = 40 lb.

In a three-phase electrical system, phase conductors carry current that is offset in time by:

Answer: 120 degrees

In a balanced three-phase system, each phase is displaced 360°/3 = 120° from the others.

An electric motor is rated at 10 horsepower. Approximately how many watts does it consume at full load? (1 hp ≈ 746 W)

Answer: 7460 W

10 hp × 746 W/hp = 7,460 W at full load.

A pneumatic cylinder uses 100 PSI air pressure on a piston with a 3-inch diameter. What is the approximate force the cylinder can exert?

Answer: 707 lb

Area = π × (1.5)² ≈ 7.07 sq-in; Force = 100 PSI × 7.07 sq-in ≈ 707 lb.