Physical Science - Chapter 13 

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