Gears, Pulleys, and Levers Flashcards

A gear system is designed to increase torque. If the driving gear has 12 teeth, which of the following driven gears would provide the greatest increase in torque?

Answer: A gear with 48 teeth

To increase torque, the driven gear must be larger (have more teeth) than the driving gear. The gear ratio, which determines the mechanical advantage, is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driving gear. A larger ratio results in a greater increase in torque. Comparing the options: 6/12=0.5 (decreases torque), 12/12=1 (no change), 24/12=2 (doubles torque), 48/12=4 (quadruples torque). Therefore, the 48-tooth gear provides the greatest torque increase.

In a pulley system with one fixed and one movable pulley supporting a load, what is the ideal mechanical advantage (IMA)?

Answer: 2

The ideal mechanical advantage (IMA) of a pulley system is equal to the number of rope segments supporting the load. In a system with one fixed and one movable pulley, the load is supported by two rope segments, thus providing an IMA of 2. The fixed pulley changes the direction of the force, while the movable pulley halves the effort needed to lift the load.

An elevator technician needs to pry open a stuck panel using a crowbar. To achieve the maximum prying force with the least effort, where should the fulcrum be placed?

Answer: As close as possible to the panel being pried

A crowbar is a Class 1 lever, where the fulcrum is between the effort and the load. To maximize the mechanical advantage (output force), the effort arm (distance from fulcrum to effort) should be as long as possible, and the load arm (distance from fulcrum to load) should be as short as possible. Placing the fulcrum very close to the panel (the load) accomplishes this, multiplying the technician's effort into a much larger prying force.

Which of the following is an example of a third-class lever, where the effort is applied between the fulcrum and the load?

Answer: A fishing rod

In a third-class lever, the effort is located between the fulcrum and the load. A fishing rod is a classic example: the fulcrum is at the end of the rod held by the angler, the effort is applied by the angler's other hand in the middle, and the load is the fish at the end of the line. A wheelbarrow and bottle opener are second-class levers, and scissors are a pair of first-class levers.

If a large gear with 60 teeth drives a small gear with 20 teeth, and the large gear makes one full rotation, how many rotations will the small gear make?

Answer: 3 rotations

The relationship between two gears is determined by their gear ratio, calculated from the number of teeth. The ratio is found by dividing the number of teeth on the driven gear by the number of teeth on the driving gear. In this case, the ratio of rotations is the inverse: (Teeth on driving gear) / (Teeth on driven gear) = 60 / 20 = 3. For every one rotation of the large driving gear, the small driven gear will rotate 3 times.

A technician uses a pulley system to lift a 200 lb motor. If the technician only has to pull with 50 lbs of force, what is the actual mechanical advantage (AMA) of the pulley system?

Answer: 4

Actual Mechanical Advantage (AMA) is the ratio of the output force (the load) to the input force (the effort). The formula is AMA = Output Force / Input Force. In this scenario, the output force is the weight of the motor (200 lbs) and the input force is the effort applied by the technician (50 lbs). Therefore, AMA = 200 lbs / 50 lbs = 4.