Levers, Pulleys, and Gears Flashcards

In the gear system shown, the driver gear (A) rotates clockwise. An idler gear (B) is placed between gear A and the driven gear (C). In which direction will gear C rotate?

Answer: Clockwise

When two gears mesh directly, they rotate in opposite directions. Therefore, if driver gear A rotates clockwise, idler gear B will rotate counter-clockwise. Since gear B (counter-clockwise) meshes with gear C, gear C will rotate in the opposite direction, which is clockwise. The primary function of a single idler gear is to make the driver and driven gears rotate in the same direction.

Which of the following lever classes always provides a mechanical advantage greater than 1, meaning the output force is always greater than the effort force?

Answer: Second-Class Lever

A second-class lever has the load (resistance) positioned between the fulcrum and the effort. This arrangement ensures the effort arm is always longer than the load arm, resulting in a mechanical advantage that is always greater than 1.

A pulley system is set up to lift a heavy engine block. The system uses multiple pulleys, and the rope is threaded so that 4 rope segments are supporting the movable block attached to the engine. Ignoring friction, what is the mechanical advantage of this system?

Answer: 4

The ideal mechanical advantage (IMA) of a pulley system is equal to the number of rope segments directly supporting the load. In this scenario, there are 4 rope segments supporting the movable block, so the mechanical advantage is 4.

A large gear with 60 teeth is driven by a small pinion gear with 20 teeth. If the small pinion gear rotates at 300 RPM, what will be the approximate speed of the large gear?

Answer: 100 RPM

The gear ratio is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driver gear (60/20 = 3:1). The speed of the output gear is the input speed divided by the gear ratio. Therefore, 300 RPM / 3 = 100 RPM. When a smaller gear drives a larger gear, speed is reduced and torque is increased.

Imagine you are using a crowbar to lift a heavy rock. You place a small stone under the crowbar to act as a fulcrum. The rock is the load, and you push down on the end of the crowbar. This is an example of which class of lever?

Answer: First-Class Lever

In a first-class lever, the fulcrum is located between the effort (your push) and the load (the rock). A seesaw and a crowbar used in this manner are classic examples of first-class levers.

In a pulley system, if you have to pull 10 feet of rope to lift a load 2 feet off the ground, what is the ideal mechanical advantage (IMA) of the system?

Answer: 5

The ideal mechanical advantage (IMA) can also be calculated as the ratio of the distance the effort moves to the distance the load moves. In this case, IMA = (Distance of effort) / (Distance of load) = 10 feet / 2 feet = 5.