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by

Jenn Wilson

on 3 February 2016

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Transcript of Work & Mechanical Advantage

In this prezi, you will learn about mechanical advantage, but before we start, we'll learn about what a machine is.
So...
What is a machine?
?
?
?
A machine is any
mechanical system
that
reduces work
.
3
By
increasing the distance
over which the force is applied.
How do machines make our work easy?
By
Increasing the force
that can be applied to an object.
A nutcracker is a machine that
increases the applied force
. When you apply the force to the handles, the jaws of the handles of the nutcracker
apply a greater force
on the nut. A person would not be able to crack a nut with their bare hands.
Example
1
2
Some examples of machines are cars and bicycles, but machines can be simple as a wrench, or a toothbrush or stairs, etc.
When someone needs to move an object to the back of the truck, they use a ramp to make work easier.
The length of the ramp is greater than the height of the truck
. By using a ramp to the
work over a longer distance
,
the person uses less force
. The distance that the cart is moved
increases and thus the force applied decreases
.
By
changing the direction
of a force.
A pulley used at the top of a flag pole
changes the direction of the force you apply
, as well as other machines. When the student in charge of the flag applies a
downward force
on the rope, an
upward force
is exerted on the flag.
What are the 2 forces needed to make a machine do work?
Input Force
The force that is
applied to a machine by YOU
Output Force
The force that the machine
applies to the object
In a car jack, the input force is the person pushing on the handle, and the output force is the jack pushing up the car.
Symbolized
Meaning
Input Force
Output Force
Fout
Forces
Fin
The force exerted on the machine
The force that the machine applies to the object

What is...
The number of times a machine increases the force exerted on it... in other words how much the machine can multiply the input force!
The ratio of the output force (F out) to the
input force (F in) determines
Mechanical Advantage=output force (in newtons) divided by input force (in newtons)

MA= Fout / Fin

When machines have a mechanical advantage of 1, this means it only changes the direction between the input and output force.
This also means the input and output forces are the same size. Sadly, these machines do not make things easier. (these are just making things more complicated)
What does it mean when a machine has
When a machine has an mechanical advantage of less than 1, this means that the output distance is greater than the input distance, or that the speed at the output force is higher than the speed at the input. In other words these machines will increase distance and speed. Some examples of machines with a mechanical advantage of less than 1 are hockey sticks, baseball bats and garden rakes.
What does it mean when a machine has a mechanical advantage less than 1?
The ideal mechanical advantage is the mechanical advantage of a machine that has no friction and would have no energy converted to the thermal energy. Because of friction, some of the work the done by the input force is converted into thermal energy.
Therefore, the work done by the output force is less than the work from the input force.
What is an ideal mechanical advantage?
Now lets put this idea to work
...
These are all examples of machines.
Simple Machines
Example of Input and Output Forces
Example of a machine that has a mechanical advantage of 1.
Example of machines that has a mechanical advantage less than 1
One last idea:

You want to make sure your machine is Efficient.

Efficiency is calculated by dividing the output work
by the input work and multiplying by 100%
What is WORK?
-scientifically WORK is only being done when a force is applied to an object and the object moves
IN THE SAME DIRECTION
as the applied force....
if a force is being applied but there is no movement; then there is NO work being done!
So how can I measure the amount of work being done on an object?
I just multiply the FORCE by the DISTANCE over which the force is applied.

W=FD
don't forget to label the units.... in this case Work is always measured in
JOULES
after this guy
When a machine has a mechanical advantage of greater that 1 then it will be a machine that multiplies force...

Good for moving/lifting heavy objects
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