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4 Science Chapter 4

Work and Machines

QuestionAnswer
actual mechanical advantage the output force divided by the input force
compound machine made of more than one simple machine
efficiency how much input work is changed to output work
fulcrum the pivot point of a lever
gears two or more wheels linked together by teeth
ideal mechanical advantage length of an inclined plane divided by the height of the plane
inclined plane a slanted surface
input force the force applied to a machine
joule the unit for work
lever an object that pivots around a fixed point
machine an object that changes the amount force or direction of the force
mechanical advantage the number of times a machine increases the applied force
output force the force a machine produces
pulley a grooved wheel with a rope
screw an inclined plane wrapped around a cylinder
tendon attaches muscle to bone
wedge a movable inclined plane
wheel and axle two circular objects fastened around an axis
work movement of an object caused by force
The mechanical advantage of a machine is the number of times a machine increases the force exerted on the machine
Which of these could be considered an inclined plane wrapped around a cylinder - lever pulley, screw, or wheel and axle? screw
If tight scissors have an efficiency of 50%, half of your work is wasted due to... friction
If you exert a force of 20 newtons to push a desk 10 meters, how much work do you do on the desk? W = F X D = 20 X 10 = 200 joules
Which of these is an example of a third-class lever - fishing pole, pliers, nutcracker, or scissors? fishing pole
Which of these is an example of work being done on an object - pushing a child on a swing, holding a door shut on a windy day so it doesn't blow open, or holding a heavy piece of wood at a construction site? pushing a child on a swing
A simple machine that might be thought of as an inclined plane that moves is a... wedge
The ideal mechanical advantage for an inclined plane is equal to the length of the incline divided by the... height of the incline
A ramp is an example of a simple machine called an... inclined plane
In order to do work on an object, the force you exert must be... in the same direction as the object's motion
Pulling down on a rope to hoist a sail on a sailboat is an example of a machine changing the direction over which a force is exerted
Which body parts are shaped like wedges? incisors (teeth)
Most of the machines in your body consist of bones and muscles and are called... levers
How can a hockey stick be considered a machine? It multiples distance
Which body parts act as the fulcrums of levers? joints
For work to be done on an object, the object must move some distance as a result of a force
Work is measured in... joules
Without friction there would be equal input and output work
Work equals force times... distance
The mechanical advantage of a machine that changes only the direction of force is... 1
A machine that utilizes two or more simple machines is called a... compound machine
The power of a light bulb that converts electrical energy at a rate of 100 joules per second is... P = W/T = 100 J/1 sec = 100 watts
The ideal mechanical advangate of a wheel and axle is equal to the... radius of the wheel divided by the radius of the axle
The wedge, screw, and lever are all... simple machines
When you raise or lower a flag on a flagpole, you are using a... pulley
What do machines do? change the amount of force you exert or the distance over which you exert the force
Power is measured in units called... watts
An ideal machine would have an efficiency of... 100%
The fixed point that a lever pivots around is called the.. fulcrum
Created by: 8thgraders
 

 



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