3What is work? Work is the product of force and distance. For a force to do work on an object, some of the force must act in the same direction as the object moves. If there is no movement, no work is done.Was any work done to lift this barbell over the weightlifter’shead?Is any work being done to keep this barbell in the air?
4What is work?Any part of a force that does not act in the direction of motion does no work on an object.
5Work = Force [N] x Distance [m] Calculating WorkWork = Force [N] x Distance [m]As the distance increases, what happens to the amount of work being done? What if it decreases?What if the force is increased? Decreased?
6Work = Force [N] x Distance [m] Calculating WorkWork = Force [N] x Distance [m]The joule [J] is the SI unit of work.When a force of 1 Newton moves an object 1 meter, 1 joule of work is done.[J]
7What is power? Power is the rate of doing work. Doing work at a faster rate requires more power. To increase power, you can increase the amount of work done in a given time, or you can do a given amount of work in less time.
8Calculating PowerYou can calculate power by dividing the amount of work done by the time needed to do the work:𝑃𝑜𝑤𝑒𝑟= 𝑤𝑜𝑟𝑘 𝑡𝑖𝑚𝑒What happens to power as time is increased? Decreased?
9Calculating Power The SI unit of power is the watt [w]. A watt is equal to 1 Joule per second.
10HorsepowerOne horsepower [hp] is equal to about 746 watts.
12Machines do WorkMachines change a force to make work easier to do. They change the size of a force needed, the direction of a force, or the distance over which a force acts.Does the jack used to lift the car increase or decrease the force applied to it?Why?
13Work Input and OutputBecause of friction, the work done by a machine is always less than the work done on the machine.
14Work Input and OutputThe force you exert on a machine is called the input force.The distance the input force acts through is known as the input distance.The work done by the input force acting through the input distance is called the work input.
16Work Input and OutputThe force that is exerted by a machine is called the output force.The distance the output force is exerted through is the output distance.The work output of a machine is the output force multiplied by the output distance.
18Mechanical AdvantageThe mechanical advantage of a machine is the number of times that the machine increases an input force.The actual mechanical advantage [AMA] is the ratio of the output force to the input force. In an ideal [IMA] situation, there would be no loss of force to friction. AMA is always less than IMA.
20Simple Machines The six types of simple machines are: The lever The wheel and axelThe inclined planeThe wedgeThe screwAnd the pulley
21LeversA lever is a rigid bar that is free to move around a fixed point.The fixed point is called a fulcrum.The input arm is the distance between the input force and fulcrum. The output arm is the distance from the fulcrum to the output force.