Physical Science: CH 14 Work and Power
Terms in this set (51)
The product of force and distance
For a force to do work on an object, some of the force must act in the same __________ as the object moves. If there is no movement, no work is done.
Any part of a force that does not act in the direction of _________ does no work on an object.
work = force x distance
The SI unit of work
When a force of 1 newton moves an object 1 meter in the direction of the force, how many Joules of work are done?
The rate of doing work is called
Doing work at a faster rate requires more __________
To increase power, you can _______ the amount of work done in a given time, or you can do a given amount of work in ______ time.
What is the equation for power?
Power = Work/Time
One horsepower (hp) is equal to about how many watts?
Machines make work easier to do. They change either: 1. _____, 2. _______, or 3. ____________.
1. the size of force needed
2. the direction of a force
3. the distance over which a force acts
If a machine increases the distance over which you exert a force, then it _________ the amount of force you need to exert.
A machine that decreases the distance through which you exert a force ________ the amount of force required.
Because of _________, the work done by a machine is always less than the work done on the machine.
The force you exert on a machine is called
The distance the input force acts through is called
The work done by the input force acting through the input distance is called
The work input equals
input force times input distance
The force that is exerted by a machine is called
The distance the output force is exerted through is the ____________
The __________ of a machine is the output force multiplied by the output distance
The number of times that the machine increases an input force is called ___
The actual mechanical advantage (AMA) equals the ratio of the output force to the _________
What is the actual mechanical advantage equation?
AMA = Output force/Input force
The mechanical advantage in the absence of friction is called _
ideal mechanical advantage (IMA)
Because friction is always present, the actual mechanical advantage of a machine is always _______ than the ideal mechanical advantage
How do you calculate Ideal Mechanical Advantage?
IMA = Input distance/Output distance
The percentage of the work input that becomes work output is the ______of a machine.
Because there is always some friction, the efficiency of any machine is always _______ than 100 percent.
What is the efficiency equation?
Eff = (Work output/Work input) x 100%
What are the six types of machines in alphabetical order?
inclined plane, lever, pulley, screw, wedge, wheel and axle
A rigid bar that is free to move around a fixed point
The fixed point the bar rotates around
The distance between the input force and the fulcrum
The distance between the output force and the fulcrum
To calculate the _______________ of any lever, divide the input arm by the output arm.
ideal mechanical advantage
A simple machine that consists of two disks or cylinders, each one with a different radius
wheel and axle
To calculate the ideal mechanical advantage of the ___________, divide the radius (or diameter) where the input force is exerted by the radius (or diameter) where the output force is exerted.
wheel and axle
A slanted surface along which a force moves an object to a different elevation
The ideal mechanical advantage of an ___________ is the distance along the ____________ divided by its change in height.
inclined plane, inclined plane
A V-shaped object whose sides are two inclined planes sloped toward each other
A thin wedge of a given length has a __________ ideal mechanical advantage than a thick wedge of the same length.
An inclined plane wrapped around a cylinder
Screws with threads that are closer together have a _________ ideal mechanical advantage.
A simple machine that consists of a rope that fits into a groove in a wheel
The ideal mechanical advantage of a ___________ is equal to the number of rope sections supporting the load that is being lifted.
A wheel attached in a fixed location
A wheel attached to an object that can be moved
A combination of fixed and movable pulleys
A combination of two or more simple machines that operate together
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