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## Arisa Timoll

on 30 April 2015

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Changing Direction

Input and Output Forces
Two forces are always applied when a machine is doing work. These two forces are called:
Input Force (F in)
Output Force (F out)
Functions of Machines
Machines make work easier in three ways:

Increasing Forces
Increasing Distance
Introduction
THANK YOU!
Usually when people think of a machine they think of more complex machines such as cars, cranes or bulldozers. All though a machine can be anything as small or as simple as a screwdriver or a wrench. A machine is any mechanical system that reduces the forces needed to finish work.
1. By increasing the force that can be applied to an object.
2. By increasing the distance over which the force is applied
3. By changing the direction of a force
Trying to crack a nut using your hands can be hard because you don't have as much force as mechanical tools
On the other hand, using a mechanical tool will make it easier to crack a nut because mechanical tools have two times more force then the average hand. (Unless you're the
hulk.
)
Picking up boxes is a harder task then using a ramp and a cart because picking up boxes with just you`re hands is directly fighting gravity oppose to using a cart and a ramp which are two simple but useful mechanical systems.
Some machines change direction from the force you apply
The pulley used at the top of a flagpole is one example, when you apply a downward force on the rope the upward force is exerted on the flag which raises it up or down.
Applied forces
For example : If you need to lift a car using a jack, the jack applies a force to the car, the force applied to the machine is
input force
and the force that the machine applies to the object is the
output force
.
** The input force is sometimes called the effort force and the output force is sometimes called the load force
Machines such as the nutcracker, ramp and car jack help to make work easier because the output force is greater then the input force (the amount by which a machine can multiply an input force is called its mechanical advantage)

since mechanical advantage is the ratio of two forces, measured in newtons, mechanical advantage has no scientific units. All though you can calculate the mechanical advantage (MA) using this equation.
Output force in newtons

Input force in newtons
MA= F out

F in
Example
When jacking up a car, Sue pushes with a force of 250 Newtons on the handle of a jack and the jack applies a force of 3000 Newtons to the car. What is the mechanical advantage of this car jack?
MA= F out
F in
MA= (3000 N)
(250 N)

MA= 12
The mechanical advantage of a machine that has no
friction is called the ideal mechanical advantage (IMA). The ideal mechanical advantage can be calculated by finding the
ratio between the distance over which the input force is exerted on the machine (d in) and the distance over which the output force is exerted on the object (d out)'
input distance
output distance
IMA= D in
D out
Suppose Pam uses a hammer to pull a nail. If she moves the handle of the hammer 30 cm and
the nail moves 5.0 cm, what is the ideal mechanical advantage of the hammer?
EXAMPLE
IMA=
D in
D out
IMA=
(30 cm)

(5.0 cm)

= 6.0
Quiz
1. Name one way a machine can work easier?
2. What is the formula for mechanical advantage?
1.By increasing the force that can be applied to an object.
2. By increasing the distance over which the force is applied
3. By changing the direction of a force
MA= F out

F in