Video Tutorial on Mechanical Aptitude Test Concepts

Gears

• Definition: Gears are interlocking wheels that provide mechanical advantage.
  • Mechanical Advantage: Depends on the gear ratio (size relation between gears).
• Standard Gear Question:
  • Pattern: If the number of gears is odd, the final gear spins the same way as the first. If even, the opposite.
• Example Problem:
  • Gear D has twice the diameter of Gear C.
  • Mechanical Advantage: Gear C's teeth (12) vs Gear D's teeth (24) = 2:1 ratio.
  • Gear Ratio: For every revolution of Gear C, Gear D revolves  times.

Horsepower

• Definitions:
  • Electrical Horsepower: 746 watts.
  • Mechanical Horsepower: 500 foot-pounds per second or 33,000 foot-pounds per minute.
• Example Problems:
  • Moving 550 lbs 1 foot over 1 second = 1 horsepower.
  • Truck weight calculation using horsepower formula.
  • Convert watts to horsepower by dividing by 746.

Liquids and Hydraulics

• Basic Rules:
  • Liquids are incompressible and conform to containers.
  • Enclosed liquid distributes pressure equally.
• Pressure Formula: Pressure = Force / Area.
  • Water pressure increases by 4.3 lbs per foot depth.
• Hydraulic Systems:
  • Movement in one vat affects another connected vat proportionally.
• Practice Problems:
  • Water pressure is greatest at the deepest point.
  • Equal containers distribute force equally.

Friction and Inefficiency

• Concept: Friction acts against motion, decreasing efficiency.
• Practice Problems:
  • Determine actual force needed considering inefficiency (e.g., pulley systems).
  • Calculate horsepower lost due to inefficiency.

Pulley Systems

• Types:
  • Fixed Pulley: Changes force direction.
  • Block and Tackle: Increases mechanical advantage.
• Mechanical Advantage Calculation:
  • Force exerted is multiplied by the number of rope segments.
• Example Problems:
  • Calculate if a person can lift a weight using given force and pulley system.

Levers

• Components:
  • Fulcrum, Resistance, and Effort.
• Classes:
  • First Class: Fulcrum between effort and resistance (e.g., seesaw).
  • Second Class: Resistance between fulcrum and effort (e.g., wrench).
  • Third Class: Effort between fulcrum and resistance (e.g., baseball bat).
• Practice Problems:
  • Identify lever classes based on images.

Work

• Definition: Force accomplishes work when displacement occurs at the force application point.
• Measurement: Joule = Newtons  Distance (Meters).
• Practice Problems:
  • Calculate work done using force and displacement.

Wedges

• Simple Machine: Triangle shape, often isosceles for equal side lengths.
• Mechanical Advantage Calculation:
  • MA = Length / Width.
• Inclined Planes:
  • Similar calculation as wedges.
• Practice Problems:
  • Calculate mechanical advantage using length and width or height.