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PH Concepts in Action CH 14
forces, work, motion, machines
36
Physics
01/16/2009

Term
 Describe a situation when a force does/produces work.
Definition
 If the force produces motion of an object in the same direction as the force, work has been done on the object.
Term
 What is the relationship between work and power?
Definition
 An increase in power can do more work, or do it faster.
Term
 Give two ways you can increase power:
Definition
 1. Produce the same amount of work in less time.2. Do more work in the same amount of time.
Term
 What is work?
Definition
 Work is force multiplied by the distance an object moves.W = f x d
Term
 What is the official SI unit of work?
Definition
 The joule.
Term
 What is the "meaning" of a joule?
Definition
 when an object is moved 1 meter (distance) using a force of 1 N.
Term
 What is power?
Definition
 The rate at at which work is completed.
Term
 What is the SI unit of power?
Definition
 The watt
Term
 What is the "meaning" of a watt?
Definition
 when work is done at the rate of 1 joule per second.
Term
 How many watts is 1 horsepower equal too?(not on test, just interesting)
Definition
 746 watts
Term
 What is the history behind the term "horsepower"?(not on test, just interesting)
Definition
 James Watt was looking for a way to compare engines to the efforts of a horse.
Term
 [image] Is work being done while he holds the weight above his head? Why or why not?
Definition
 No because the weights are not moving.
Term
 You exert a vertical force of 7 newtons to lift a box to a height of 1.0 meter in a time of 2.0 seconds. How much power is used to lift the box?
Definition
 36 W , make sure to show your work and use all units.
Term
 When the floor "supports" you, with a normal force, is it doing work? Why or why not?
Definition
 No, because you are not moving!
Term
 Machines can make easier by doing one of 3 things. Name the three things a machine might change.
Definition
 They change the size of a force needed, the direction of a force, or the distance over which a force acts.
Term
 How is the work input related to the work output in a machine?
Definition
 Because of friction, the work done by a machine is always less than the work done on the machine.
Term
 Define a machine.
Definition
 A machine is an object that changes the size, direction or distance over which the force is applied.
Term
 input force
Definition
 the amount of force applied TO the machine(Hint: I= I am pushing/pulling where)
Term
 What is input distance?(Not on test)
Definition
 The distance over which the input force is applied. (How far you push or pull)
Term
 What is input work?(Not on test)
Definition
 The amount of work you put into a machine. This is calculated by taking the input force and multiplying by the input distance.
Term
 What is output force?(Not on test)
Definition
 The amount of force that the machine produces.
Term
 What is output distance?(Not on test)
Definition
 The distance over which the machine exerts a force.
Term
 What is output work?(Not on test)
Definition
 The amount of work performed by the machine.
Term
 True or False:A machine allows you to do less work and still produce more work.
Definition
 False, a machine will never produce more work that you put into it.
Term
 How does the actual mechanical advantage of a machine compare to its ideal mechanical advantage?
Definition
 The actual MA is always less than the ideal MA.
Term
 Why is the efficiency of a machine always less than 100 percent?
Definition
 Because friction will always reduce the actual mechanical advantage of a machine.
Term
 What is the mechanical advantage of a machine?
Definition
 MA is the number of times a machine multiples the input force. So if the machine makes your force of 2N become 4N of output force, its MA is 2 (2x greater)
Term
 What is the Actual Mechanical Advantage of a machine?
Definition
 Fout/Fin
Term
 What is Ideal Mechanical Advantage?(Not on test)
Definition
 Ideal Mechanical Advantage is the mechanical advantage of a machine, minus any friction.
Term
 What is the efficiency of a machine?(Not on test)
Definition
 The percentage of the work input that becomes work output is the efficiency of a machine.
Term
 Name the six types of simple machines.
Definition
 Lever, Pulley, Screw, Wedge, Incline Plane, Wheel and Axle
Term
 What is a lever?
Definition
 A simple machine of a rigid bar with a fixed point.
Term
 Draw a lever and label the input force, input distance, fulcrum, output force, and output distance.
Definition
 [image]
Term
 How many types of levers are there?Draw a picture of each:
Definition
 There are 3 types of levers. [image]
Term
 How many types of pulley systems are there?Draw a diagram of each: (not on test)
Definition
 [image]
Term
 What is a compound machine?
Definition
 A machine made up of 2 or more different types of simple machines.
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