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Chapter 5 ps

This document discusses simple machines and their uses. It defines six types of simple machines: lever, pulley, wheel and axle, inclined plane, screw, and wedge. For each machine it explains how it works and provides examples. It also covers concepts like work, energy, power, mechanical advantage, efficiency, and how machines conserve energy. Simple machines allow us to do work more easily by reducing the amount of force needed.

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Chapter 5 Simple machines
WORK  The transfer of energy that occurs when a force makes an object move  In order for work to be done a force must make an object move
2 Conditions of work  1. The object must move  2. Movement must be in the same direction as the force applied
Work and Energy  When work is done there is always a transfer of energy  Energy is the ability to do work  When you do work on an object, you increase its energy
Calculating work  Work (J) = Force (N) x distance (m)  W = Fd
Power  The rate at which work is done  SI unit for power is the Watt (W)  P (watts) = Work (J)/Time (s)  Usually expressed in kilowatts
Power and Energy  Power is the rate at which energy is transferred  Power (w) = energy (J)/Time (s)
Machine  A device that makes doing work easier
Simple Machines  A Machine that does work with only one movement of the machine  6 types of simple machines: lever, pulley, wheel and axle, inclined plane, screw, and wedge
Lever  A bar that is free to pivot or turn around a fixed point  The fixed point is called a fulcrum  There are 3 classes of levers
Pulley  A grooved wheel with a rope, chain, or cable running along the groove  The axle of the pulley acts as the fulcrum  Fixed and movable  Fixed IMA = 1, Movable IMA = 2
Block and Tackle pulley  A system of pulleys consisting of both fixed and movable pulleys  IMA is equal to the number of rope segments that support the weight
Wheel and Axle  consists of a shaft or axle attached to a larger wheel.  The wheel and axle rotate together  Examples: Pencil sharpeners, door knobs, screw drivers, faucet handles
Inclined Plane  A sloping surface, such as a ramp.  Reduces the amount of force required to do work  IMA = Length of slope (m)/Height (m)
Screw  An inclined plane wrapped in a spiral around a cylindrical post  IMA is related to the spacing of the threads
Wedge  An inclined plane with one or two sloping sides  It changes the direction of the input forces
Compound Machine  Two or more simple machines that operate together  A car is a compound machine
Compound Machines
2-Forces Involved in Work 1. Input Force: The force that is applied to the machine. (effort force) Given the symbol Fin 2. Output Force: The force applied by the machine. Given the symbol Fout
2-Types of Work done on a Machine 1. Input Work: The work done by you on the machine. Given the symbol Win 2. Output Work: The work done by the machine. Given the symbol Wout
Conserving Energy  A machine cannot create energy, so… Wout can never be greater than Win
Which means that…  Wout will always be less that Win …  because friction changes some of the energy to heat.
Ideal Machine  A machine without friction.  Win = Wout
Mechanical Advantage  The ratio of the output force to the input force.  Can be calculated using the following equation.
Efficiency  A measure of how much of the input work put into a machine is change into useful output.
Efficiency Cont… • The efficiency of an ideal machine is 100 percent. • The efficiency of a real machine is always less than 100 percent.
How can machines be made more efficient??? • by adding a lubricant, such as oil or grease, to surfaces that rub together.