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# Inspiration from the siege

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Inspiration from the siege

The ancients broke the city gate, put the big tree trunk on the pulley, and crashed into the city gate.

The kinetic energy of the soldiers was amplified ten times because the rolling friction coefficient was 1/10.

Suppose the soldiers were carrying the wood and ramming it against the city gate, using the same amount of force, the effect would be ten times worse than using a pulley.

The calculation is as follows: The work done by the soldiers W=FS

When there is a pulley, F=1/10ma (m represents the trunk mass, a=10 meters/second^2), and the work distance S=20 meters. W1=1/10m×10×20=20m

Without a pulley, the tree was lifted directly into the city gate. W2=m×10×20=200m

It is very intuitive to see: under the same acceleration, the tree trunk rushes out the same distance, and the kinetic energy of the tree trunk hitting the door is the same, E=1/2mv^2=1/2m(at)^2=1/2m×( 10×2)^2=200m (According to the final velocity formula v=at; according to S=1/2at^2, find t=2)

The work done by the soldiers was 10 times different.

It can be seen that the use of pulleys is not only labor-saving but also energy-saving. Soldiers only need to put in 1/10 of the work to get 10 times the kinetic energy. According to this principle, wouldn’t the door to the perpetual motion machine

be knocked open? !

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Of course, everything you wrote is Nonsense!

A pulley is a type of lever. It has a mechanical advantage in Force, but it does not reduce the amount of work done!

Basically, it trades a reduction in applied force for an increase in the distance over which work must be done.

In your example, if the Force advantage is 1/10, the distance over which work is done, increases by a factor of 10.

Without the pulley the Force is Mα, where α is 10 m/s^2 and the work is done over a distance of 20 meters. Work = F x D = 200 M using your confusing terminology.

Using correct terminology, Mass is in kg, Force = kg x 10 m/s^2, Work = F x D = kg x 10 m/s^2 x 20 m

Work = 200 kg x m^2/s^2

With the pulley the Force is 1/10 Mα and the work is done over a distance of 200 meters.

Work = F x D = 1/10 kg x 10 m/s^2 x 200 meters = 200 kg x m^2/s^2

The work done is exactly the same with or without the pulley.

( I use M for the Mass so as not to confuse Mass with distance in meters m )

These calculations are basic mechanics, so I suspect you just came here to troll us.

Moved to silly claims.

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The soldier only pushed 20 meters (work distance), but the tree trunk and pulley had the kinetic energy to move 200 meters.

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4 hours ago, icaninvent1 said:

The soldier only pushed 20 meters (work distance), but the tree trunk and pulley had the kinetic energy to move 200 meters.

Either you are trolling or you need to study some basic mechanics, or both.

A pulley is a type of lever; it can be used to leverage force at the cost of distance, or it can be used the opposite way, to leverage distance at the cost of force.

What it cannot do is leverage work/energy.

Your statement "The soldier only pushed 20 meters (work distance), but the tree trunk and pulley had the kinetic energy to move 200 meters" makes no sense.

You are mixing up work distance with kinetic energy.

Read my post again or consult a book on basic mechanics.

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This is exactly what traditional physics misses, and I've been studying it for 40 years.

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After 40 years of studying physics you still don't understand how a stick works? That is all a lever is; just a stick.

The Neanderthals knew how to use a stick to move large rocks and drop them down from a height on the backs of Mammoths to bring those large and dangerous animals down. They didn't have any physics books to consult; they figured out leverage all by themselves.

Now I am sure you are trolling because nobody can be so thick they can't understand a stick.

If you are not trolling, I feel sorry for you.

This thread is closed.

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