 When a force causes an object to move in the same direction of the force that is being applied  Does effort always equal work?  Calculating Work › Work = force x distance or › W = F*d  Units as Force is measured in newtons (N) and distance in meters (m), thus work is measured in joules (J)

 A weight lifter lifts 500-N weight at distance of 2 m from the floor to a position over his head. How much work does he do? Where w = F*d

 Using a force of 50 N, you push a computer cart 10 m across a classroom floor. How much work did you do?  Work Work

 What is a machine › A device that helps you do work  Simple machine › A machine that uses only one movement › Ex: Screwdriver, inclined plane, wedge, wheel, axel  Compound Machine › A combination of simple machines › Ex: can opener  How do machines make things easier › Increase the amount of force › Can change the direction of the force

 Mechanical Advantage › The number of times the applied force is increased by a machine › Mechanical advantage = output force/input force › Or MA = F o /F i  Work In and Work Out › In simple machines the input and output force do work › Ex: Can opener the output force is at the blade puncturing the can › Ideal world there is no friction and work in = work out

 Pulley – an object with a groove, like a wheel, with a rope or chain running through the groove › Changes the direction of the input force › Pulley Pulley 100 N Simple pulley Combination of Pulleys 50 N 100 N Quiz 2 stop point

 Lever – a rod or plank that pivots about a fixed point › Can increase force or increase the distance over which the force is being applied › 3 classes of lever  1 st class: Fulcrum – located between the input and output force (usually used to increase force)  2 nd class: the output force is between the input force and the fulcrum (output force always greater than the input)  3 rd class: the input force is between the output force and the fulcrum (MA < 1, increase the distance over which the input force is applied) Lever Lever, Wheel and AxelWheel and Axel

 Inclined Plane – sloped surface, sometimes called a ramp. › Allows for heavy lifting by using less force over a greater distance › Work remains the same whether a ramp is used or a straight lift › The longer the ramp the less force is needed to move the object › Where in ancient history could ramps have been useful? Inclined plane

 Wedge – moving inclined plane with one or two sloping sides › Changes the direction of the input force › Ex: knife, axe  Screw – an inclined plane wrapped around a post. › Changes the direction of the force you apply › Ex: winding road around a mountain