Work and Machines

13A Work and Mechanical Advantage

• Work and Power

  • Work: the energy transferred to a system by an external force when it acts on the system to move it

  • Power: the rate of doing work

• Machines

  • Simple Machines: a basic mechanical device that changes the magnitude, direction, or distance traveled of the force used when doing work

  • Inclined Plane: simple machine that consists of a plane whose opposite ends are at different heights

  • Mechanical Advantage: the amount by which a simple machine multiplies an input force to produce an output force

• Mechanical Advantage and Efficiency

  • Ideal Mechanical Advantage: the mechanical advantage for an ideal machine (100% efficient) with no friction

  • Actual Mechanical Advantage: the mechanical advantage that accounts for all mechanical losses sustained through using a machine

  • Efficiency: a comparison of the amount of usable energy remaining after a process with the original amount of energy that went into the process

13B Lever

• Simple Machine: Lever

  • Lever: a simple machine that consists of a rigid bar that turns about a pivot point (the fulcrum)

  • Fulcrum: the point about which a lever pivots or rotates

• How Levers Work

  • Torque: a force that tends to cause a rotation about a pivot point

• Classifying Levers

  • First-Class Lever: a lever in which the fulcrum is between the input and output forces

  • Second-Class Lever: a lever in which the output force is between the input force and the fulcrum

  • Third-Class Lever: a lever in which the input force is between the output force and the fulcrum

13C Wheel and Axle

• Simple Machine: Wheel and Axle

  • Wheel and Axle: a simple machine consisting of a wheel with a rod running through its axis that acts as the pivot point

• Gear: a simple machine that consists of a wheel with teeth on its perimeter that mesh with similar teeth of other gears to do work

• Pulley: a simple machine that consists of a wheel and axle system with a groove around the perimeter of the wheel in which a rope, cable, or belt moves with the wheel as it rotates

• Pulley Systems

  • Single pulleys

  • Block and tackle

13D Inclined Plane

• Simple Machine: Inclined Plane

  • Inclined Plane: a simple machine that consists of a plane whose opposite ends are at different heights

• Compound Machine: a machine that combines two or more simple machines