Simple Machines

SIMPLE MACHINE

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MACHINES

Work is …………………….……

What is a machine?........

Why use

machines?.........

WORK•is the transfer of energy

from one physical distance to another

•Measured in Joules

W = F x dWork = Force x Distance

MACHINES

• …..any device or instrument that helps you do something

machines make work we do easier

WORK = FORCE x DISTANCE

• WORK INPUT WORK OUTPUT

•INPUT = OUTPUT

EFFORTFORCE

DISTANCE

OUTPUTFORCE

DISTANCE

Multiply the force

Multiply the distance

Change in Direction

TYPES OF WORKA.INPU

T work that goes into the machine

needs effort force

B. OUTPUT

Work done by the machine

Resistance Force

Machines do not increase work output

“Work output is never greater than work input”

WORK = FORCE x DISTANCE

• WORK INPUT WORK OUTPUT

•INPUT = OUTPUT

EFFORTFORCE

DISTANCE

OUTPUTFORCE

DISTANCE

Multiply the force

Multiply the distance

Change in Direction

Work in = Work out• Work input (force to move something

over a distance) • Work output (force from the machine

to move something over a distance)

• Machines make work easier because they change either the _________ or _________of the force put into the machine.

What is Mechanical Advantage?

Number of times a machine multiplies the effort force

Tells how much force is gained by using machine

Mechanical Advantage = Output Force

Input Force

Examples:

Inclined Plane:

M.A. = Load

Effort

= 5N/0.2N

= 25

Pulley:

M.A. = Load

Effort

= 6.5N/1.5N

= 4

so … …. Half the force needed = MA of 2

One third the force = MA of 3

A MA of less than 1 = increase force, but over a smaller distance (faster but harder)

Output force

Input forcex 100%

Efficiency of the machine =

•Expressed as a percentage

EFFICIENCY

LEVERS• Simple machines used to lift

weights

First Class LeversAn example of this type is a seesaw.

Second Class Lever The difference from the first class lever is that the fulcrum is on the end, instead of in the middle.

Third Class Lever The load is the fish; the handle end is the fulcrum.

•The force you exert on the machine is called the input force or the effort force. The force exerted by the machine is called the output force or the resistance force.

•If you compare the input force to the output force, you can determine the advantage of using a machine. A machine’s mechanical advantage is the number of times a force exerted on a machine is multiplied by the machine.

A machine makes work easier by changing the amount of force you exert, the distance over which you exert your force, or the direction in which you exert your force.

Pulley

• Changes the direction of the force and the amount of force.

Lever

Increase input force and direction (eg prying open a can of paint)

INCLINED PLANE

Inclined Plane

- A simple machine that makes it easier to move a heavy object to a higher or lower elevation.

- It reduces the amount of force needed to lift the object by increasing the distance.

INCLINED PLANE

Increases the distance so reduces the force

Ideal MA = Length Height

•The Egyptians used inclined planes to build the pyramids.

WEDGES

- A wedge is a simple machine shaped like an inclined plane.

- It is like a portable inclined plane.

SCREWSA screw is a cylinder with an

inclined plane wrapped around it.

Wedge and Screw

•Force is applied over a longer distance

•Think of the screw being a long inclined plane!!!

WHEEL AND AXLE

- made up of two circular objects of different sizes

Smaller Object (axle)

Larger Object (wheel)

Wheel and Axle

•Wheel = Large diameter•Axle = Small diameter

•This is a Force Multiplier – over a longer distance