Calculating Compound Gears Quiz

Gears

• A pair of wheels with teeth that interlink, transferring turning motion and force to each other.
• Characteristics of gears:
  • Work together in gear trains (2 or more gears)
  • Can change the speed, force, and direction of motion
  • Alternate the direction of spin
  • Integrate with other gears, or with a linkage (e.g., sprockets)

Multiplying and Reducing Gears

• Multiplying gears: larger driving gear increases turning speed in the system
• Reducing gears: smaller driving gear decreases turning speed in the system

Mechanical Advantage (MA)

• Calculated as output force (load) / input force (force you apply)
• MA = 1 (no mechanical advantage) when input force equals output force
• Example: Justin uses a wheelbarrow to move 600 N bricks with 120 N (MA = 5)

Mechanical Advantage (MA) of Pulleys

• MA = number of pulleys in the system
• Diameter of pulleys does not affect MA

Mechanical Advantage (MA) of Screws

• MA = π (diameter of screw head) / lead (distance of one full rotation)
• Example: MA of a screw with 9mm radius and 3mm pitch is approximately 14.4

Mechanical Advantage (MA) of Inclined Planes

• MA = length of slope / height of the slope
• Example: MA of a screw with 9mm radius and 3mm pitch is approximately 3

Mechanical Advantage (MA) of Gears/Gear Trains

• MA = gear ratio (GR) = number of teeth of driven gear / number of teeth of driver gear
• Example: MA of a gear train with 30 teeth and 20 teeth is approximately 1.5

Mechanical Advantage (MA) of Other Simple Machines

• Speed ratio measures how the speed of an object is affected by a machine
• Example: inclined plane makes it possible to lift heavy objects using a smaller force, but requires moving the object over a longer distance

The Effects of Friction on MA

• Friction can reduce the efficiency of a machine and decrease MA
• One way to reduce friction is to lubricate the machine's moving parts

Calculating Pressure

• Pressure = force / area
• Example: pressure on a man's foot when a woman steps on his foot with her heel is approximately 520,000 Pa (Pascals)

Pressure in Fluids

• Hydraulic system uses a liquid under pressure to move loads
• Pneumatic system uses air under pressure to move loads
• Pascal's Law states that an enclosed fluid transmits pressure equally in all directions

Hydraulic Advantage

• Hydraulic system creates a mechanical advantage as a result of Pascal's Law on pressure
• MA is force multiplied throughout the system