Wheels, Axles, and Rotation Flashcards

A flywheel stores energy by spinning at high speed. Which property MOST determines how much energy it can store?

Answer: Its rotational speed and mass distribution

Rotational kinetic energy depends on both the moment of inertia (how mass is distributed) and the square of rotational speed.

Gear A (driver, 12 teeth) meshes directly with Gear B (36 teeth). Gear A rotates at 900 RPM. What is Gear B's speed?

Answer: 300 RPM

Speed of Gear B = (teeth of A / teeth of B) × speed of A = (12/36) × 900 = 300 RPM.

A hand truck (dolly) has small wheels. Replacing them with larger-diameter wheels would primarily:

Answer: Make it easier to roll over obstacles and reduce rolling resistance

Larger wheels have a higher ratio of radius to obstacle height, allowing them to roll over bumps more easily, and larger wheels generally have lower rolling resistance.

In a clock, the minute hand completes one revolution per hour. The hour hand completes one revolution every 12 hours. What is the gear ratio between the mechanisms driving each hand?

Answer: 12:1

The minute hand turns 12 times for every 1 turn of the hour hand, so the gear ratio is 12:1.

A wheel spins at constant speed. A point on the outer rim of the wheel compared to a point halfway to the center has:

Answer: Twice the linear speed

Linear (tangential) speed = angular speed × radius; at twice the radius, the rim point travels twice the linear speed.

Which of the following is an example of a wheel-and-axle simple machine?

Answer: A screwdriver turning a screw

A screwdriver handle acts as the wheel (large radius) and the shaft acts as the axle (small radius), giving mechanical advantage for turning screws.

A drive shaft transfers power from an engine to the rear wheels of a truck. If the drive shaft develops a crack near the center, the MOST likely result is:

Answer: Vibration, noise, and eventual loss of power to the rear wheels

A cracked drive shaft causes imbalance leading to vibration and noise, and may fail completely, cutting power transmission to the driven wheels.