the

Why Invention of the wheel is important

welcome to the video tutorials of

mechanisms by mechanism Euler

without a doubt the invention of the

will is one of the most important

inventions in human history why was it

so important when you do a google search

on the topic you will find many

explanations which explain the benefits

of the will but they do not mention the

core reason of the importance of the

wheel with this video I will try to

include my two cents on the subject

first let's ask ourselves what the power

requirement to move a load from point A

to B on a flat surfaces you can assume

any valid value for the load or any

other input you need to calculate this

power it is paradoxical that the power

we consume to carry the load is zero

that does not make sense

it is 0 because the

of the power in the engineering field is

vector product of force and velocity as

you can see in the slide shown the force

vector and velocity vector have 90

degree angle between them

this makes the result of this vector

product zero you may say okay I got it

but then why do I get tired when I carry

a heavy load the answer is you will get

tired even if you don't walk a heavy

load will put a lot of pressure on your

skeleton and your muscles

the solution to this problem is to carry

the load indirectly we all dragged heavy

loads rather than to carry them this

behavior allows us to put the weight on

the ground and we overcome the friction

force while we're dragging this friction

force is comparably smaller than the

weight of the actual load to reduce the

friction force even more we have to

create some mechanism to drag the load

one solution used by many American

Indians is the Travoy shown in this

photo now

let's investigate the problems of using

a travois in this design the friction

between the load and the ground is

reduced by having X shaped poles on the

horseback this reduces the friction

substantially but it does put some load

on the horse's shoulders

let's do a leverage calculation of this

mechanism a hundred kilogram load put in

the middle of the pole

where the midpoint is the point between

the poles attached on the horseback and

touch the ground assuming that the pole

length from shoulder to ground is three

meters this arrangement will put a 50

kilogram load on the shoulders of the

horse for a 300 kilogram load it will

jump to 150 for the horse apparently

this is not a very good arrangement for

the horse

also the pole ends that are touching the

ground are subject to heavy wear and

tear

ordinary wheelbarrows are similar in

operation to the Travoy with a slight

improvement the addition of the will at

the end reduces the friction to a

minimum this is due to the fact that the

rolling resistance is much smaller than

dragging friction

however the operator is burdened with

carry a fraction of the load we can do

much better than that

a much better solution comes from China

where fulcrum load weight and reaction

force all lined up on a vertical line

passing through the will touching the

ground

this arrangement removes any load on the

person pushing it and enable him to

carry much heavier loads

they even went further to use sales to

help push whenever the wind was coming

from the desired direction

the same idea has been used by Americans

to carry large logs with ease by using

big wheels where the load was hanging

from the axle of the wheels

here is another view of the big wheel

in short to carry loads by will or

slides the load should be on the axle

for two-wheeled carriages or between

axles for four wheeled carriages same is

true for slides

this slide shows that four horses can

pull enormous weight while one horse

will not be able to carry even one log

on its back

here is a picture of an Egyptian chariot

notice that the Pharaoh and rider are

standing on the axle which removes the

load from the horse also the large six

spoked will substantially reduce rolling

friction with the ground the horses

could run full speed with ease the

chariot was considered the battle tank

of its time it allowed Egyptians to

expand their empire

however there is a small catch while the

wheeled carriage has had big advantages

on the flat surface they have one major

disadvantage on the hilly roads when a

person carrying a load uphill there is a

component of its weight and the load

dragging him backwards multiplication of

this vector with velocity will not be

zero this time hence the power

requirement to carry the load and person

himself will be proportional with this a

passing vector higher the climbing angle

the higher will be the power requirement

the same thing happens to bicycles cars

and trucks while they are on an uphill

road they not only carry the load they

also carry the additional weight of the

equipment whether it's a car or a truck

we have to build flat highways whenever

it is possible by building tunnels or

bridges this will reduce fuel

consumption of cars and trucks

substantially by shortening the distance

and eliminating opposing force component

if trucks wear climbing

if you are using single two-wheeled cart

make sure that the center of gravity

passes through the axle of the cart or a

little bit or donkeys side as you can

see apposite shift of the load will put

poor donkey in very awkward position

in short the will takes the heavy load

from our shoulder and put all the weight

on the ground with overcoming slight

rolling resistance it enables us to

easily carry very heavy loads

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