==Work is done on an object when you apply a force to it and it moves in the direction of that force.==
==When you do work on an object, you change its energy. This is an important idea known as the Work-Energy Theorem. (The work is always EQUAL to the energy)==
==Power is the rate at which work is done. As we said in class, it’s a measure of how quickly (or slowly) you do work on an object.==
==A machine is any device that makes work easier.==
^^There are three (3) ways machines can make work easier to do:^^
==With any machine, there is always a tradeoff. The tradeoff in a machine is that it can increase the strength of your input force OR increase the distance over which it acts==, but it CAN NOT do both at the same time.
==Mechanical advantage is a measure of how much a machine increases your input force. It also tells us which of the three ways a machine is making work easier:==
==The efficiency of a machine is a percentage of how much useful work the machine can actually do.== It’s always less than 100%.
^^No machine can ever be 100% efficient, because friction is always present.^^
==Simple Machines do work by using only ONE MOVEMENT.==
==There are six (6) kinds of simple machines==: ^^Levers, wheel & axle, screws, wedges, pulleys, and inclined planes.^^
With any simple machine, there is always a TRADEOFF- either a machine can increase the amount of our input force, or make our input force last a longer distance, but it ==CAN NOT DO BOTH.==
==A lever is a simple machine that pivots, or rotates, around a fixed point.==
==The mnemonic “Frogs Lay Eggs” can help you remember the three classes of levers:==
@@A good example of a 1st class lever is a seesaw.@@
@@A good example of a 2nd class lever is a wheelbarrow.@@
@@A good example of a 3rd class lever is a broom@@.
With a 1st class lever, the mechanical advantage could be greater than, equal to, or less than 1. ^^This means that a 1st class lever could increase our input force, change the direction of our input force, or make our^^ ^^input force last a longer distance.^^
With a 2nd class lever, the mechanical advantage is always greater than 1. ^^So a 2nd class lever will always increase the amount of our input force.^^
With a 3rd class lever, the mechanical advantage is always less than 1. ^^So a 3rd class lever will always increase the distance our input force acts, making it last longer.^^
==A wheel and axle is an axle attached to the center of a wheel. Both rotate together. Wheel/Axles always increase the amount of our input force.==
@@Ex: Door Knob@@
==An inclined plane is a flat, sloped surface that makes lifting loads easier. It also increases our input force but makes us apply the force a longer distance (the tradeoff).==
@@Ex: Ramp@@
==A wedge helps us by cutting or separating two objects. It’s a sloped surface that moves.==
@@Ex: Teeth@@
==A screw is an inclined plane that is wrapped around a cylinder.==
@@Ex: Threads on a light bulb@@
==A pulley is a grooved wheel with a rope/chain/cable wrapped around it. It helps us lift loads and change the direction of force applied.==
Ex:
\n ==A compound machine is two or more simple machines that are put together to help us do work. Compound machines are less efficient than simple machines at doing work.==
@@Ex: Scissor@@