2 Lesson 1- Work and Power What is work? any time a force is exerted on an object that causes the object to movethe object must move in the same direction in which the force is exerted.No movement of object = no work done no matter how much force is used
16 What does a machine do? Makes work easier by changing the amount of force your exert ORchanging the distance over which you exert your force ORchanging the direction in which you exert your force
17 Machines don’t change the amount of work you do, but they do change the way you do the work.
18 Changing ForceIf a machine allows you to use less input force, you must apply that force over a greater distance.
19 Changing Force Work = Force X Distance Let’s Say: My force is 5 N and the distance is 2 m;5 N x 2 m = 10 J of workIf the amount of work stay the same,a decrease of force means an increase of distance.If I put 2N of force, then my distance would be 5m to equal 10 J of work.
20 Changing DistanceIf a machine allows you to move your input force over a shorter distance, than you need to apply a greater input force.
22 Change DirectionSome machines don’t change in either force or distance, they change the direction of the force.Small input forcelarge input distancelarge output distanceSmall output force
23 Mechanical AdvantageThe number of times a machine increases a force exerted on it.The ratio of output force to input forceMechanical Advantage = output forceinput force
24 What happens when you increase Force? When the output force is greater than the input force - mechanical advantage > 1YES15N / 10N = 1.5Greater
25 What happens when distance increases? When a machine increases distance, the output force (machine’s force) is less than the input force (your force).Mechanical advantage is < 1
26 What happens when direction changes? Input force = output forceMechanical advantage is 1.The larger the mechanical advantage, the easier a machine makes your work.
27 What is efficiency?The machine’s (output) work is always less than your (input) work because the machine has to overcome the force of friction.The less work a machine has to do to overcome friction, the more efficient it is.
28 To calculate efficiency... Output workX 100%Input work
29 Inclined Planes and Levers Lesson 3Inclined Planes and Levers
30 Simple Machines: Inclined Planes - Flat sloped surface Wedge - device that is thick on one end and tapers to a thin edge at the otherScrew - be thought of as an inclined plane wrapped around a cylinder.
32 Levers: Rigid bar that is free to pivot, or rotate on a fixed point. That fixed point is called a fulcrumTypes of levers are classified according to the location of the fulcrum relative to the input and output forces.