simple machines and gears and their mechanical advantage.ppt

8/9/2019 Simple Machines and Gears and their mechanical advantage.ppt

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imple Machines:

imple Machines:

Gears, Velocityears, Velocity

Ratios and

atios and

Mechanicalechanical

Advantage

dvantage


2/11

What is a simple

hat is a simple

machine?achine?

A device which uses A device which usesbasic mechanisms tobasic mechanisms tomake work easier for themake work easier for theuser.user. Example: Lifting a heavyExample: Lifting a heavy

box with a rope and pulleybox with a rope and pulleysystemsystem

Simple machines areSimple machines arefound in manyfound in many

transportation devicestransportation devicessuch as the following:such as the following: CarsCars icyclesicycles !rains!rains


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What are gears and why

hat are gears and why

are they so useful?re they so useful?

"ears are toothed"ears are toothed

wheels which interlockwheels which interlock

to form simpleto form simple

machines.machines.

!he tighter the #oint$ the!he tighter the #oint$ the

less chance of slippingless chance of slipping

"ears range in si%e but"ears range in si%e but

the important number isthe important number is

how many teeth a gearhow many teeth a gear

has.has.


4/11

What is a gear ratio?

hat is a gear ratio?

A gear ratio is the ratio between the driver gear A gear ratio is the ratio between the driver gear

&the one being powered' and the driven gear&the one being powered' and the driven gear

&the one connected to the driver'&the one connected to the driver' "ear (atios are expressed as fractions and can be"ear (atios are expressed as fractions and can be

written a number of ways.written a number of ways. ) to *) to *

)+*)+*

):*):*

Always remember that the driven gear will turn in Always remember that the driven gear will turn in

the opposite direction of the driver gear the opposite direction of the driver gear


5/11

What is a pulley?

hat is a pulley?

A wheel with a grove carved around its A wheel with a grove carved around its

circumference in which a rope or belt iscircumference in which a rope or belt is

placed to drive the wheel.placed to drive the wheel. ,ulleys are used in a number of applications,ulleys are used in a number of applications

including:including:

ElevatorsElevators

CranesCranes

Automobiles Automobiles


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A ulley ystem

ulley ystem


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!raw"ac#s of ulleys

raw"ac#s of ulleys

,ulleys work great as long as the belt which,ulleys work great as long as the belt which

connects them is tight and both pulleys areconnects them is tight and both pulleys are

aligned.aligned.

,ulleys tend to slip when too much strain is placed,ulleys tend to slip when too much strain is placedon the system.on the system.


8/11


9/11

What is Velocity Ratio

hat is Velocity Ratio

&VR'?

VR'?

0hen calculating for velocity or speed$ it is0hen calculating for velocity or speed$ it is

best to have a ratio in which the driver gear isbest to have a ratio in which the driver gear is

larger than the driven gear.larger than the driven gear. 1or maximum speed you should always have a1or maximum speed you should always have a

larger driver gear+pulley paired with a smallerlarger driver gear+pulley paired with a smaller

driven gear+pulley.driven gear+pulley.


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What is Mechanical

hat is Mechanical

Advantage &MA'?dvantage &MA'?

(eciprocal of velocity(eciprocal of velocity

ratio.ratio.

2echanical advantage2echanical advantage

describes how much workdescribes how much work

can be done based on thecan be done based on the

input.input.

3f my system re-uired me3f my system re-uired me

to apply 45 pounds ofto apply 45 pounds offorce into the system to liftforce into the system to lift

)55 pounds of weight$ 3)55 pounds of weight$ 3

have used 2A.have used 2A.


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o which do % want?

o which do % want?

6igher velocity ratios are better when working6igher velocity ratios are better when working

on straight and level surfaces which areon straight and level surfaces which are

smooth.smooth. Always remember that with a high 7( your system Always remember that with a high 7( your system

will have very low power.will have very low power.

6igher mechanical advantage systems are6igher mechanical advantage systems are

better with inclines surfaces that are bumpy.better with inclines surfaces that are bumpy. 0ith a high 2A your system will produce more0ith a high 2A your system will produce more

power$ but will move slower.power$ but will move slower.

simple machines and gears and their mechanical advantage.ppt

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