Homework help - Models.

[Relative]

1. what forces act on the cylinder? no need for figures - just names, points of action, and directions

Gravity, mass, the East of the cylinder will always be pulled down, the west of the cylinder will always be forced upwards/opposite.

 

All actions have an opposite reaction.

 

 

this vaguely?

I know my angles are off.

You want me put in x y z vectors etc?

Are you trying to explain a fulcrum?

[imatfaal]

gravity - check

mass - since when was mass a force?

the East of the cylinder will always be pulled down, the west of the cylinder will always be forced upwards/opposite

 

This is very important - wrong - but very important. This is why we model things to look at various ways things can be understood - and to work out why one is a better approximation that the other.

 

So gravity is one force, what is the other (clue it is not slipping/sliding - it is rolling)?

[Relative]

gravity - check

mass - since when was mass a force?

 

 

This is very important - wrong - but very important. This is why we model things to look at various ways things can be understood - and to work out why one is a better approximation that the other.

 

So gravity is one force, what is the other (clue it is not slipping/sliding - it is rolling)?

Rolling is an action, not a force, the other force involved would be levitation, weight shifted by greater angle?

The South East point having greater mass.

Like a glass of water when we tilt it.

Edited August 29, 2014 by Relative

[imatfaal]

Rolling is an action, not a force, the other force involved would be levitation, weight shifted by greater angle?

The South East point having greater mass.

 

What single difference is there between a cylinder rolling and a cylinder sliding down a hill?

 

Levitation? What is that when it is at home?

Not sure what weight shifted by greater angle means.

And the cylinder is uniform so no section has greater weight - this is the sort of simplification or assumption that modelling requires.

You are looking for two more forces - and in all three cases you should be able to show a point where the force can be seen as acting and a direction of this force.

[Relative]

 

What single difference is there between a cylinder rolling and a cylinder sliding down a hill?

 

Levitation? What is that when it is at home?

Not sure what weight shifted by greater angle means.

And the cylinder is uniform so no section has greater weight - this is the sort of simplification or assumption that modelling requires.

You are looking for two more forces - and in all three cases you should be able to show a point where the force can be seen as acting and a direction of this force.

angle of incline, levitation, leverage.

 

I only can see gravity has the force involved, centripetal, and mass been shifted.

 

 

Could you enlighten me on the other two acting forces?

It would be off balance.

''What single difference is there between a cylinder rolling and a cylinder sliding down a hill? ''

 

Grip...

Edited August 29, 2014 by Relative

[imatfaal]

...

 

Grip...

 

Also known as friction. A rolling cylinder is turning on its axis but a sliding cylinder is not; for something to start turning there needs to be a force acting at a distance from its centre of mass (a torque).

 

There is one more force - what stops the cylinder sinking into the ground?

[Relative]

Or you would say friction.

 

 

Also known as friction. A rolling cylinder is turning on its axis but a sliding cylinder is not; for something to start turning there needs to be a force acting at a distance from its centre of mass (a torque).

 

There is one more force - what stops the cylinder sinking into the ground?

Yes I know friction is grip.

 

Density of the surface it is rolling down, the ''viscosity'' of the surface?

 

If it was in soft mud, it would slowly slide down the mountain.

 

and I presume velocity, Like stone skipping on a pond.

 

However is velocity a force?

 

If not , no idea?

[imatfaal]

velocity is not a force.

 

We call the force that a surface produces on an object the Normal - it is what stops you sinking through the floor, what stops your fingers going through the key when you type etc.

 

http://en.wikipedia.org/wiki/Normal_force

 

Can you now draw a simple diagram to show the forces which act?

[Relative]

velocity is not a force.

 

We call the force that a surface produces on an object the Normal - it is what stops you sinking through the floor, what stops your fingers going through the key when you type etc.

 

http://en.wikipedia.org/wiki/Normal_force

 

Can you now draw a simple diagram to show the forces which act?

I am even more confused now I have looked at the normal force link you provided.

 

I see nothing but gravity , been the only force.

 

''In mechanics, the normal force is the component, perpendicular to the surface (surface being a plane) of contact, of the contact force exerted on an object''.

 

The surface does not exert a force on an object, gravity holds the object on the surface?

 

If the surface has a less dense structure, a different ''viscosity'', <muddy water compared to water>, <soil compared to rock>,

 

Then gravity will try to pull you through it.

 

The only force is centripetal to all mass, and by off balance the cylinder roles or slides.

 

I thought my diagram was simple sorry, and shows the same has the normal force diagram link but without the maths?

[Fuzzwood]

If the normal force of a floor you stood on would be weaker than the gravity force exerted upon you, you would fall through the floor. If you are still standing still, yet there is gravity acting upon you, there must be a counteracting force, ergo the normal force.

Edited August 29, 2014 by Fuzzwood

[Relative]

X axis will always try to fall.

 

If the normal force of a floor you stood on would be weaker than the gravity force exerted upon you, you would fall through the floor. If you are still standing still, yet there is gravity acting upon you, there must be a counteracting force, ergo the normal force.

There is no force in a floor, gravity holds me to the floor, the floor is dense?

Does a cylinder not fall down a hill and rolling or sliding is just the action?

[imatfaal]

X axis will always try to fall.

 

What is this trying to say? This is physics - we try to explain things in simple terms and in terms that can be quantified. The x axis is a mathematical tool - it doesn't try to do anything

 

There is no force in a floor, gravity holds me to the floor, the floor is dense?

 

Fuzzwood just explained this - as does the wikipage. Why do you contradict on the basis of no knowledge.

 

Does a cylinder not fall down a hill and rolling or sliding is just the action?

 

This is the idea of modelling - we look at simplified scenarios and see what we can gain from them. To answer your question - no a cylinder does not simply fall down a hill, there is an imbalance of forces which causes the cyclinder to accelerate and in some cases to turn.

[Relative]

 

What is this trying to say? This is physics - we try to explain things in simple terms and in terms that can be quantified. The x axis is a mathematical tool - it doesn't try to do anything

 

 

Fuzzwood just explained this - as does the wikipage. Why do you contradict on the basis of no knowledge.

 

 

This is the idea of modelling - we look at simplified scenarios and see what we can gain from them. To answer your question - no a cylinder does not simply fall down a hill, there is an imbalance of forces which causes the cyclinder to accelerate and in some cases to turn.

Re-direction of mass .

 

Why do I contradict, because I look at the articles, and they either jump out and are instantly correct, or the complete opposite.

 

My thoughts on the cylinder was instantaneous.

 

 

 

 

All mass is attracted to a central point, centripetally , by gravity, all objects with no surface contact in our atmosphere fall, just because you put a slope in the way it does not mean that object is not still falling, but been redirected.

 

X axis on my diagram, the entire axis would fall, and if no other elements affected it, it would stay falling linear like an arrow.

 

So this is why I contradict.

 

I like accuracy.

 

 

My cylinder still wants to fall?

[Fuzzwood]

X axis will always try to fall.

 

There is no force in a floor, gravity holds me to the floor, the floor is dense?

Does a cylinder not fall down a hill and rolling or sliding is just the action?

And here we go again. Disproving something established in physics because you don't grasp the theory. Take it from me that there is a force acting upon you from the floor which vector is opposite to the direction of the vector of gravity and with an equal magnitude.

 

 

 

Re-direction of mass .

 

Why do I contradict, because I look at the articles, and they either jump out and are instantly correct, or the complete opposite.

 

My thoughts on the cylinder was instantaneous.

 

cent.jpg

 

 

 

All mass is attracted to a central point, centripetally , by gravity, all objects with no surface contact in our atmosphere fall, just because you put a slope in the way it does not mean that object is not still falling, but been redirected.

 

X axis on my diagram, the entire axis would fall, and if no other elements affected it, it would stay falling linear like an arrow.

 

So this is why I contradict.

 

I like accuracy.

cy.jpg

 

 

My cylinder still wants to fall?

 

Yes it does. If you let go of the beaker, it, and its contents, will certainly fall. However, the force that the glass is exerting on the cylinder is preventing it from falling.

Edited August 29, 2014 by Fuzzwood

[Relative]

once velocity slows down my cylinder returns to the correct direction?

 

And here we go again. Disproving something established in physics because you don't grasp the theory. Take it from me that there is a force acting upon you from the floor which vector is opposite to the direction of the vector of gravity and with an equal magnitude.

 

 

 

 

Yes it does. If you let go of the beaker, it, and its contents, will certainly fall. However, the force that the glass is exerting on the cylinder is preventing it from falling.

I cant see that has a force, I can only see that has a density difference, if you said that the object exerted pressure on the surface, by the attractive force of gravity, then I could understand that.

[imatfaal]

Re-direction of mass .

 

Why do I contradict, because I look at the articles, and they either jump out and are instantly correct, or the complete opposite.

 

My thoughts on the cylinder was instantaneous.

 

....

 

So this is why I contradict.

 

This is why most people here would describe your actions as unscientific.

 

Please get back to simple sentences and concepts - why are you introducing water when you haven't even been able to draw a simple diagram with the forces labelled? You have to be able to walk before you can run.

 

As Fuzzwood has now said twice - there is and must be a force exerted on you by the ground beneath your feet otherwise you would be accelerating into the earth. You have already mentioned newtons third law - think what this entails.

[Relative]

Gravity wants to pull the cylinder through the beaker?

 

The beaker is been held by force a hand, stopping both the glass and ball falling?

 

And i still am confused what model we are making?

[Fuzzwood]

Then answer this. What is a force?

[Relative]

 

This is why most people here would describe your actions as unscientific.

 

Please get back to simple sentences and concepts - why are you introducing water when you haven't even been able to draw a simple diagram with the forces labelled? You have to be able to walk before you can run.

 

As Fuzzwood has now said twice - there is and must be a force exerted on you by the ground beneath your feet otherwise you would be accelerating into the earth. You have already mentioned newtons third law - think what this entails.

Understood , but the opposite reaction is redirection , and I have labelled the forces sever times, been gravity.

 

There is no other force involved unless you add propulsion.

 

I am scratching my head, I must be thick or something.

 

Ok,

 

I will try be simple, with my questions, what force does the ground apply on the cylinder?

 

Is it not the cylinder applying the force to the ground, the force been surface pressure?

Then answer this. What is a force?

A force can have several meanings ,

 

But in this context, ''change'' by applying

 

 

The direction of the cylinder is forced to change by angle of the dense matter, if we removed the hill the cylinder would continue to fall.

 

The cylinder is trying to force its way through the matter, but the matter is dense, and the cylinder does not have impact velocity.

 

 

So the only possible direction for the cylinder to take, is redirection.

 

The only actual force is gravity, and the object pressing against the surface, trying to go through that surface.

 

Creating surface pressure.

[Ophiolite]

The cylinder 'pushes' at the ground; the ground 'pushes' back.

 

Have you never walked down a flight of stairs and reached the bottom one step earlier than you expected? If so, what did you experience? Can you relate that to this conversation?

[Relative]

In this diagram you just cause mass shift, weight shift.

 

The cylinder 'pushes' at the ground; the ground 'pushes' back.

 

Have you never walked down a flight of stairs and reached the bottom one step earlier than you expected? If so, what did you experience? Can you relate that to this conversation?

The ground does not push back.

 

Yes I have missed a few stairs in my time, I experience the force of impact, my weight moving at a velocity and impacting with the floor,

 

The shock wave from my weight would send waves into the floor that are absorbed by density , or if the grounds ''viscosity'' is a weak density, the energy is slowly absorbed, until the ground under me becomes more compact , dense.

 

this happens yes?

[physica]

For some reason I can't attach pictures, look at the diagram I sent you via personal message relative

Edited August 29, 2014 by physica

[swansont]

If the hill was ice, then there would be little friction and the cylinder would slide down the hill gaining momentum, I do not understand what is the importance of this, what is the findings we are looking for?

 

There would be too many variables to consider , meaning an inconclusive test.

 

 

Friction tells you whether the cylinder will roll or slide, and those two cases give very different results.

 

Part of model-building is deciding what terms to discard as being too small. If the model doesn't work, one reason can be that an effect that was assumed to be small was actually important.

[Fuzzwood]

The ground does not push back.

Yet it quite rapidly stopped any downward motion you had. In essence decellerating your mass till your velocity was 0.

 

Remind me how the force of gravity was defined again? Oh right, it was F_g = m * g (mass times the acceleration caused by gravity). How is that any different than the phenomenon I explained above this paragraph?

[Relative]

For some reason I can't attach pictures, look at the diagram I sent you via personal message relative

Thank you for the diagram why does the radius vector point uphill?