Wheels, Axles, and Rotation Flashcards

Two bicycles, A and B, are traveling side-by-side at the exact same speed. Bicycle A has larger wheels than Bicycle B. Which statement is true about the rotation of the wheels?

Answer: The wheels of Bicycle A are rotating at a slower RPM.

To cover the same linear distance per unit of time (speed), a wheel with a larger circumference needs to complete fewer revolutions than a wheel with a smaller circumference. Therefore, the larger wheels of Bicycle A rotate at a slower RPM to keep the same speed as Bicycle B.

Gear A is turning clockwise and is meshed directly with Gear B. Gear B is on the same axle as Gear C, which is smaller. Gear C is meshed directly with Gear D. In which direction is Gear D turning?

Answer: Clockwise

If Gear A is clockwise, Gear B (meshed with A) must turn counter-clockwise. Since Gear C is on the same axle as Gear B, it also turns counter-clockwise. Because Gear D is meshed with Gear C, it must turn in the opposite direction, which is clockwise.

In a simple wheel and axle system, such as a winch used to lift a heavy bucket from a well, where is the effort force typically applied to gain a mechanical advantage?

Answer: To the handle on the outer edge of the wheel.

Mechanical advantage is achieved by applying effort over a greater distance to move a load over a shorter distance. In a winch, applying force to the handle (on the circumference of the wheel) turns the smaller axle. Since the wheel has a much larger radius than the axle, the force required is significantly less than the weight of the load.

A mechanic is trying to loosen a stubborn, rusted bolt. After failing with a standard wrench, which of the following actions would be MOST effective in helping them loosen the bolt?

Answer: Using a wrench with a longer handle or adding a pipe to extend it.

Torque is the rotational force needed to turn the bolt, calculated as the applied force multiplied by the perpendicular distance from the pivot point (the bolt's center). By increasing the length of the handle (the distance), the mechanic can generate the same amount of torque with less applied force, making it easier to loosen the stubborn bolt.

Which of the following best describes the fundamental purpose of a solid axle in a simple two-wheel cart?

Answer: To connect the wheels and ensure they rotate together at the same rate.

The axle is a rigid rod that connects the two wheels. Its primary function is to transfer rotational motion and force, compelling both wheels to spin at the same speed. This ensures the cart moves in a straight line when pushed or pulled.

How does using wheels and an axle make it easier to move a heavy object across a flat surface compared to simply dragging it?

Answer: By converting high sliding friction into much lower rolling friction.

Dragging an object requires overcoming sliding friction, which is the high-resistance force between two surfaces scraping against each other. Wheels replace this with rolling friction (or rolling resistance), which occurs at the axle and the point of contact with the ground. This type of friction is significantly lower than sliding friction, requiring less effort to move the object.