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science ch. 4 section 1

Terms in this set (55)

machines make doing work easier or faster by changing the _________ needed to do the work
force
work
force applied through a distance
another definition
work is the energy transferred when a force makes an object move
formula for work
w=fd
unit ofr work
joule (J)
3 condition in order to do work
a force must be applied to the object
the object must move
the movement of the object must be in direction of the force
when work is done, a _____________ occurs
transfer of energy
when are you doing work on an object
when you are physically touching an object and applying force
when the force and motion of an object are ____________ the maximum amount of work is being done
parallel (same direction)
when the force and motion of the object are ___________ then there is no work being done
perpendicular
when the force and motion of the object are ____________ less than maximum work is being done
at an angle
a machine is a device that changes the _____________ or increases the ___________ from work
force, motion
simple machine
a machine that does work with only one movement of the machine
6 simple machines
lever
screw
pulley
wheel and axle
inclined plane
wedge
compound machine
a combination of two or more simple machines
efficiency
the ratio of output work to input work
alternate definition for efficiency
a measure of how much work put into a machine is changed into useful work output by the machine
no machine can increase both _____ and _____ at the same time
force, speed
you always put more ____ into a machine then you get out of the machine
work
no machine is !00% efficient because of ________
friction
formula for efficiency
output work/input work x 100
ideal machine
a theoretical machine in which the amount of work put into the machine is equal to the amount of work you get out of the machine
machines _________ the speed of work getting done
increase
machines multiply/increase __________
force
machines change the __________ of a force
direction
we can describe the effectiveness of a machine at increasing ________ by its ______________
force, mechanical advantage
mechanical advantage
a machine's ability to make work easier by making an output force greater than input force
input force
the force that a person or device applies to a machine
output force
the force that the machine applies to another object
mechanical advantage formula
output force/input force
if mechanical advantage is less than 1
the machine is not making wok easier
if mechanical advantage is greater than 1
the machine is making work easier
What is the force distance trade off?
when you apply a force on a machine/object for a longer distance to do the work needed. The force you put on the machine/object is multiplied by the machine but only moves a small distance.
lever
a bar that is free to pivot or turn around a fixed point
fulcrum
The fixed point around which a lever pivots
input arm
the distance between the input force and the fulcrum
output arm
the distance between the output force and the fulcrum
first class lever
fulcrum is located between the input force and output force
the output force is on the opposite side of input force
second class lever
the output force is between the fulcrum and the input force
output force is greater than input force
third class lever
the input force is between the fulcrum and the output force
the output force is less than the input force, but the distance of the input force increases
pulley
a grooved wheel with a rope, chain, or cable running along the groove that is used to lift objects
fixed pulley
first class lever that changes input force but does not increase input force
movable pulleys
increased/multiplied input force with one end of rope is fixed and the wheel can move
fixed pulley
IMA-1
movable pulley
!MA-2
Block and tackle
Fixed pulley and a movable pulley are used together
IMA is equal to the number of rope segments supporting by weight
wheel and axle
a simple machine consisting of a shaft or axle attached to the center of a larger wheel, so that the wheel and axle rotate together
wheel and axle IMA
rw/ra
lever IMA
Lin/Lout
inclined plane
a sloping surface that reduces the amount of force required to do work
inclined plane IMA
length of slope/height of slope
screw
an inclined plane wrapped in a spiral around a cylindrical post
screw IMA
threads closer together, less force, turns more
threads farther apart, more force, turns less
wedge
inclined plane with 2 sloping sides that changes direction of input force
wedge IMA
l/w
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