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chapter: 14 section: 2
Terms in this set (30)
machines/devices such as: cars, trucks, with many moving parts powered by an engine or an electric motor are what we would consider machines, but what are other kinds?
1. - using a pair of scissors to cut a piece of paper
2. - using a broom to sweep
3. - cutting your food with a knife
what is a scientific machine?
a machine is simply a device that makes doing work easier
can a sloping surface be a machine?
even though machines make work easier what do they not increase?
the amount of work you need to do
instead of decreasing the amount of work you need to do, what do machines change?
machines change the way in which you do work
what happens when you use a machine?
you exert a force over some distance
you exert a force to move a rake, the force that you apply on a machine is the input force. the work you do on the machine is equal to the input force times the distance over which your force is applied, the work that you do on the machine is the input work
what does a rake do scientifically?
a rake for example exerts a fire to move leaves
you life the handles of a wheelbarrow, the force that you apply on a machine is the input force. the work you do on the machine is equal to the input force times the distance over which your force is applied, the work that you do on the machine is the input work
what does the wheelbarrow do scientifically?
being a machine, when you exert force on it, it moves a certain distance
what is an input force?
the force that you apply on a machine is the input force
what is an output force?
the force that the machine applies is the output force
what do machines also do involving work?
by force to move an object over some distance
what is another word for a machines force?
why is a machines force otherwise known as resistance force?
because the machine is trying to overcome some resistance
what is always true about when you use a machine?
the output work can never be greater than the input work
what is the advantage of using a machine?
a machine makes work easier by changing the amount of force you need to exert, the distance over which the force is exerted or direction in which you exert your force
how do some machines make doing a job easier?
by reducing the force you have to apply to do the job
what is mechanical advantage?
how much larger the output force is compared to the input force is the mechanical advantage
what is the mechanical advantage equation?
mechanical advantage equals output force in newtons, over input force in newtons
MA= f out / f in
does mechanical advantage have units?
why does mechanical advantage not have units?
because it is the ratio of two numbers with the same units
some machines allow you to exert your force over a shorter distance, give an example
when you rake leaves you move you hands a short distance but at the end of the rake it moves over a longer distance
what is the mechanical advantage of raking leaves?
the MA of this time of machine is less than one because the output force is less that the input force
give an example where it is easier to apply a force in a certain direction
it is easier to pull down on the rope than to pull up on it
true or false:
some machines enable you to change the direction of the input force
what would the MA be in a pulling rope situation?
equal to one because the output force is equal to the input force
what is efficiency?
the efficacy of a machine is the ratio of the output work to the input work and can be calculated from the equation
what is the efficiency equation?
efficiency in perfect equals output work in joules over input work in joules times one hundred percent
eff= w out / w in x 100
what is true of the amount of friction is reduced?
the efficiency of the machine increases
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