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Simple Machines: Gears, Velocity Ratios and Mechanical Advantage

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Simple Machines: Gears, Velocity Ratios and Mechanical Advantage

- A device which uses basic mechanisms to make work easier for the user.
- Example: Lifting a heavy box with a rope and pulley system

- Simple machines are found in many transportation devices such as the following:
- Cars
- Bicycles
- Trains

- Gears are toothed wheels which interlock to form simple machines.
- The tighter the joint, the less chance of slipping
- Gears range in size but the important number is how many teeth a gear has.

- A gear ratio is the ratio between the driver gear (the one being powered) and the driven gear (the one connected to the driver)
- Gear Ratios are expressed as fractions and can be written a number of ways.
- 1 to 3
- 1/3
- 1:3

- Always remember that the driven gear will turn in the opposite direction of the driver gear

- Gear Ratios are expressed as fractions and can be written a number of ways.

- A wheel with a grove carved around its circumference in which a rope or belt is placed to drive the wheel.
- Pulleys are used in a number of applications including:
- Elevators
- Cranes
- Automobiles

- Pulleys are used in a number of applications including:

- Pulleys work great as long as the belt which connects them is tight and both pulleys are aligned.
- Pulleys tend to slip when too much strain is placed on the system.

- A simple equation is used to find the ratio of your gearing system
- Number of Teeth on the Driven Gear / Number of Teeth on the Driver Gear.
- Size of the driver pulley/ Size of the driven pulley

- When calculating for velocity or speed, it is best to have a ratio in which the driver gear is larger than the driven gear.
- For maximum speed you should always have a larger driver gear/pulley paired with a smaller driven gear/pulley.

- Reciprocal of velocity ratio.
- Mechanical advantage describes how much work can be done based on the input.
- If my system required me to apply 50 pounds of force into the system to lift 100 pounds of weight, I have used MA.

- Higher velocity ratios are better when working on straight and level surfaces which are smooth.
- Always remember that with a high VR your system will have very low power.

- Higher mechanical advantage systems are better with inclines surfaces that are bumpy.
- With a high MA your system will produce more power, but will move slower.