Wheels, Axles, and Rotation Flashcards

A compound gear train has three gears in sequence: Gear 1 (40 teeth) drives Gear 2 (10 teeth), which shares an axle with Gear 3 (30 teeth), which drives Gear 4 (15 teeth). What is the overall speed ratio (Gear 4 speed / Gear 1 speed)?

Answer: 8:1

Stage 1 ratio: 40/10 = 4; Stage 2 ratio: 30/15 = 2; overall = 4 × 2 = 8, so Gear 4 spins 8 times faster than Gear 1.

A crossed belt connects two pulleys. If the driving pulley rotates clockwise, the driven pulley rotates:

Answer: Counterclockwise

A crossed belt reverses the direction of rotation, so a clockwise driver produces counterclockwise motion in the driven pulley.

Which change would MOST increase the torque output of a wheel-and-axle system when effort is applied at the wheel?

Answer: Increasing the wheel's radius

Torque output increases when the effort arm (wheel radius) is larger relative to the load arm (axle radius), so increasing wheel radius boosts mechanical advantage.

A bicycle has a front chainring with 48 teeth and a rear sprocket with 16 teeth. How many times does the rear wheel rotate for each pedal revolution?

Answer: 3

Speed ratio = driver teeth / driven teeth = 48/16 = 3, so the rear wheel makes 3 revolutions per pedal revolution.

A wheel rolling uphill loses speed compared to rolling on flat ground (same force applied). This is primarily because:

Answer: Gravity adds a resisting force component along the slope

On an incline, gravity acts against motion along the slope, requiring additional force to maintain speed, which slows the wheel if force is unchanged.

Two identical wheels are connected by their axles via a rigid rod (like a car axle). When the vehicle turns left, which wheel must rotate faster?

Answer: The right wheel

In a left turn, the right (outer) wheel travels a longer arc and must rotate faster than the inner left wheel.

A pulley system uses a fixed pulley only. What mechanical advantage does it provide for lifting a load?

Answer: 1:1

A single fixed pulley only changes the direction of force, not its magnitude, providing a mechanical advantage of 1:1.