Easy enough to picture, a big block of metal that is raised then let fall onto a pile.

If however instead of a solid block whose base is entirely atop the pile, say you had the exact same wieght but configured in the shape of a cannon barrel that is lowered over the pile so that the pile goes up the barrel and hits the base of the cannon.

If the base of the cannon and the base of the block are raised to the same height before being dropped would they have the same effect, as basically, in the cannon, a lot of the weight is not falling as far.

AwesomeO said:

Easy enough to picture, a big block of metal that is raised then let fall onto a pile.

If however instead of a solid block whose base is entirely atop the pile, say you had the exact same wieght but configured in the shape of a cannon barrel that is lowered over the pile so that the pile goes up the barrel and hits the base of the cannon.

If the base of the cannon and the base of the block are raised to the same height before being dropped would they have the same effect, as basically, in the cannon, a lot of the weight is not falling as far.

The centre of mass of the cannon would be lower than the centre of mass of the block so it would not be as effective as the block. ie the potential energy of the cannon would be lower.

Can you draw us a picture? Is the cannon pointing downward?

Peak Warming Man said:

AwesomeO said:

Easy enough to picture, a big block of metal that is raised then let fall onto a pile.

If however instead of a solid block whose base is entirely atop the pile, say you had the exact same wieght but configured in the shape of a cannon barrel that is lowered over the pile so that the pile goes up the barrel and hits the base of the cannon.

If the base of the cannon and the base of the block are raised to the same height before being dropped would they have the same effect, as basically, in the cannon, a lot of the weight is not falling as far.

The centre of mass of the cannon would be lower than the centre of mass of the block so it would not be as effective as the block. ie the potential energy of the cannon would be lower.

surely if the masses are the same and the distance that it falls are the same then the difference in PE to KE would be insignificant?

Boris said:

Peak Warming Man said:

AwesomeO said:

Easy enough to picture, a big block of metal that is raised then let fall onto a pile.

If however instead of a solid block whose base is entirely atop the pile, say you had the exact same wieght but configured in the shape of a cannon barrel that is lowered over the pile so that the pile goes up the barrel and hits the base of the cannon.

If the base of the cannon and the base of the block are raised to the same height before being dropped would they have the same effect, as basically, in the cannon, a lot of the weight is not falling as far.

The centre of mass of the cannon would be lower than the centre of mass of the block so it would not be as effective as the block. ie the potential energy of the cannon would be lower.

surely if the masses are the same and the distance that it falls are the same then the difference in PE to KE would be insignificant?

The point is it doesn’t fall as far.
The presumption being that the centre of mass is used to establish the same height of the blocks before dropping.

Peak Warming Man said:

Boris said:

Peak Warming Man said:

The centre of mass of the cannon would be lower than the centre of mass of the block so it would not be as effective as the block. ie the potential energy of the cannon would be lower.

surely if the masses are the same and the distance that it falls are the same then the difference in PE to KE would be insignificant?

The point is it doesn’t fall as far.
The presumption being that the centre of mass is used to establish the same height of the blocks before dropping.

reading the OP the distance of the fall are the same.

Thinking about it some more, all of the cannon would fall the same height, just that more of its mass is under the top of the pile than the block which is entirely on top of the pile…

Or another way to think about it, it would take less energy to raise the cannon pile driver base 1 metre because you are not raising the full wieght of the cannon above 1 metre, but the block, all of it would need to be raised 1 metre.

AwesomeO said:

Or another way to think about it, it would take less energy to raise the cannon pile driver base 1 metre because you are not raising the full wieght of the cannon above 1 metre, but the block, all of it would need to be raised 1 metre.

the canon is all one piece so all of it is raised one metre. the only difference is the distance from the centre of mass of the two types of weight and the centre of the Earth.

Boris said:

Peak Warming Man said:

Boris said:

surely if the masses are the same and the distance that it falls are the same then the difference in PE to KE would be insignificant?

The point is it doesn’t fall as far.
The presumption being that the centre of mass is used to establish the same height of the blocks before dropping.

reading the OP the distance of the fall are the same.

Yes, I worded it badly.
If the two blocks are lifted from their contact point on the pile by the same amount and then dropped the cannon will have less effect on the pile because it’s centre of mass is lower.

AwesomeO said:

Easy enough to picture, a big block of metal that is raised then let fall onto a pile.

If however instead of a solid block whose base is entirely atop the pile, say you had the exact same wieght but configured in the shape of a cannon barrel that is lowered over the pile so that the pile goes up the barrel and hits the base of the cannon.

If the base of the cannon and the base of the block are raised to the same height before being dropped would they have the same effect, as basically, in the cannon, a lot of the weight is not falling as far.

Neglecting air effects, it’s still the same force, the same impulse, the same effect.

INCLUDING air effects, this might actually be slightly less effective, as the air in the cannon has to squeeze past the pile to escape: it’s presence will slow the drop slightly. But in the fair dinkum department I’d expect that to be an insignificant effect.

F=MA

dv said:

AwesomeO said:

Easy enough to picture, a big block of metal that is raised then let fall onto a pile.

If however instead of a solid block whose base is entirely atop the pile, say you had the exact same wieght but configured in the shape of a cannon barrel that is lowered over the pile so that the pile goes up the barrel and hits the base of the cannon.

If the base of the cannon and the base of the block are raised to the same height before being dropped would they have the same effect, as basically, in the cannon, a lot of the weight is not falling as far.

Neglecting air effects, it’s still the same force, the same impulse, the same effect.

INCLUDING air effects, this might actually be slightly less effective, as the air in the cannon has to squeeze past the pile to escape: it’s presence will slow the drop slightly. But in the fair dinkum department I’d expect that to be an insignificant effect.

it’s physics DV, all physics is done in a vacuum.

;-)

I just want to be clear, this is what we are talking about right? Normal piledriver on the left, cannon piledriver on the right. Same weight, same drop in each case, but in the cannon case, the pile is enveloped by the walls of the cannon.

If so, then my previous answer stands. Effect should be the same except that air effects might slow the fall of the cannon.

dv said:

I just want to be clear, this is what we are talking about right? Normal piledriver on the left, cannon piledriver on the right. Same weight, same drop in each case, but in the cannon case, the pile is enveloped by the walls of the cannon.

If so, then my previous answer stands. Effect should be the same except that air effects might slow the fall of the cannon.

Yes, that’s it.

dv said:

I just want to be clear, this is what we are talking about right? Normal piledriver on the left, cannon piledriver on the right. Same weight, same drop in each case, but in the cannon case, the pile is enveloped by the walls of the cannon.

If so, then my previous answer stands. Effect should be the same except that air effects might slow the fall of the cannon.

we are in agreement DV. goodo.

Boris said:

dv said:

I just want to be clear, this is what we are talking about right? Normal piledriver on the left, cannon piledriver on the right. Same weight, same drop in each case, but in the cannon case, the pile is enveloped by the walls of the cannon.

If so, then my previous answer stands. Effect should be the same except that air effects might slow the fall of the cannon.

we are in agreement DV. goodo.

In that image, a cannon pile driver would be a better design, you don’t have to lift your infrastructure as high for the same result?

AwesomeO said:

Boris said:

dv said:

I just want to be clear, this is what we are talking about right? Normal piledriver on the left, cannon piledriver on the right. Same weight, same drop in each case, but in the cannon case, the pile is enveloped by the walls of the cannon.

If so, then my previous answer stands. Effect should be the same except that air effects might slow the fall of the cannon.

we are in agreement DV. goodo.

In that image, a cannon pile driver would be a better design, you don’t have to lift your infrastructure as high for the same result?

and the reason star picket drivers have the design they do. so you don’t need to be 3m high to drive them in

AwesomeO said:

Boris said:

dv said:

I just want to be clear, this is what we are talking about right? Normal piledriver on the left, cannon piledriver on the right. Same weight, same drop in each case, but in the cannon case, the pile is enveloped by the walls of the cannon.

If so, then my previous answer stands. Effect should be the same except that air effects might slow the fall of the cannon.

we are in agreement DV. goodo.

In that image, a cannon pile driver would be a better design, you don’t have to lift your infrastructure as high for the same result?

Which would b why the cannon pile driver was invented?

There may be some friction losses with the canon type depending on how close the fit is with the pile. But you probably already knew that.

AwesomeO said:

Boris said:

dv said:

I just want to be clear, this is what we are talking about right? Normal piledriver on the left, cannon piledriver on the right. Same weight, same drop in each case, but in the cannon case, the pile is enveloped by the walls of the cannon.

If so, then my previous answer stands. Effect should be the same except that air effects might slow the fall of the cannon.

we are in agreement DV. goodo.

In that image, a cannon pile driver would be a better design, you don’t have to lift your infrastructure as high for the same result?

Yeah that makes sense

party_pants said:

There may be some friction losses with the canon type depending on how close the fit is with the pile. But you probably already knew that.

this is a physics question, no friction.

Boris said:

party_pants said:

There may be some friction losses with the canon type depending on how close the fit is with the pile. But you probably already knew that.

this is a physics question, no friction.

the pile drivers need to be spherical to complete the trifecta.

Boris said:

and the reason star picket drivers have the design they do. so you don’t need to be 3m high to drive them in

So you’ve never bothered getting one then.

Boris said:

Boris said:

party_pants said:

There may be some friction losses with the canon type depending on how close the fit is with the pile. But you probably already knew that.

this is a physics question, no friction.

the pile drivers need to be spherical to complete the trifecta.

…and a blackbody radiator for the quadrella.

sibeen said:

Boris said:

and the reason star picket drivers have the design they do. so you don’t need to be 3m high to drive them in

So you’ve never bothered getting one then.

nah, get a mate to hold the picket while i belt it in with a sledge.

sibeen said:

Boris said:

Boris said:

this is a physics question, no friction.

the pile drivers need to be spherical to complete the trifecta.

…and a blackbody radiator for the quadrella.

Boris said:

sibeen said:

Boris said:

and the reason star picket drivers have the design they do. so you don’t need to be 3m high to drive them in

So you’ve never bothered getting one then.

nah, get a mate to hold the picket while i belt it in with a sledge.

He must be a really good mate.

roughbarked said:

Boris said:

sibeen said:

So you’ve never bothered getting one then.

nah, get a mate to hold the picket while i belt it in with a sledge.

He must be a really good mate.

actually it was the reverse. i was holding the picket. plus you don’t take a full swing at it. there is a technique. and i trusted him, though he doubted himself. he didn’t hit me.

The cannons CoM is lower than the CoM of the block and therefore it has less potential energy than the block.

Peak Warming Man said:

The cannons CoM is lower than the CoM of the block and therefore it has less potential energy than the block.

90cm over 6371km isn’t going to make much difference.

Boris said:

Peak Warming Man said:

The cannons CoM is lower than the CoM of the block and therefore it has less potential energy than the block.

90cm over 6371km isn’t going to make much difference.

Doesn’t matter what the units are and the 90 is just happenstance and is for nothing more than to show the lifts are the same.

Boris said:

Peak Warming Man said:

The cannons CoM is lower than the CoM of the block and therefore it has less potential energy than the block.

90cm over 6371km isn’t going to make much difference.

Hold on, Boris. If I calculate the energy in a mass I do so for its height above ground, not its height above the centre of the earth,

Is a penis a poofters pile driver?

bob(from black rock) said:

Is a penis a poofters pile driver?

It may alarm you Bob but homosexuals are not the only people to engage in anal sex.

Witty Rejoinder said:

bob(from black rock) said:

Is a penis a poofters pile driver?

It may alarm you Bob but homosexuals are not the only people to engage in anal sex.

How do women do it?

bob, not appropriate.

bob(from black rock) said:

How do women do it?

Google will help.

Witty Rejoinder said:

bob(from black rock) said:

How do women do it?

Google will help.

Google or gargle?

Boris said:

party_pants said:

There may be some friction losses with the canon type depending on how close the fit is with the pile. But you probably already knew that.

this is a physics question, no friction.

Not sure what you think physics means…

Peak Warming Man said:

The cannons CoM is lower than the CoM of the block and therefore it has less potential energy than the block.

The actual change in PE will be the mass times g times the drop.

Witty Rejoinder said:

bob(from black rock) said:

Is a penis a poofters pile driver?

It may alarm you Bob but homosexuals are not the only people to engage in anal sex.

Also, “piledriver” is a sexual position that is also used in vaginal sex.

dv said:

Boris said:

party_pants said:

There may be some friction losses with the canon type depending on how close the fit is with the pile. But you probably already knew that.

this is a physics question, no friction.

Not sure what you think physics means…

…ideal physics…a vacuum, no friction and a spherical cow.

sibeen said:

Boris said:

Peak Warming Man said:

The cannons CoM is lower than the CoM of the block and therefore it has less potential energy than the block.

90cm over 6371km isn’t going to make much difference.

Hold on, Boris. If I calculate the energy in a mass I do so for its height above ground, not its height above the centre of the earth,

surely this applies?

https://en.wikipedia.org/wiki/Gravitational_acceleration

Boris said:

sibeen said:

Boris said:

90cm over 6371km isn’t going to make much difference.

Hold on, Boris. If I calculate the energy in a mass I do so for its height above ground, not its height above the centre of the earth,

surely this applies?

https://en.wikipedia.org/wiki/Gravitational_acceleration

The PE is just height x mass x G.

Mass and G stay constant, the centre of mass has lowered therefore the height has lowered.

sibeen said:

Boris said:

sibeen said:

Hold on, Boris. If I calculate the energy in a mass I do so for its height above ground, not its height above the centre of the earth,

surely this applies?

https://en.wikipedia.org/wiki/Gravitational_acceleration

The PE is just height x mass x G.

Mass and G stay constant, the centre of mass has lowered therefore the height has lowered.

big G or small g?

sibeen said:

Boris said:

sibeen said:

Hold on, Boris. If I calculate the energy in a mass I do so for its height above ground, not its height above the centre of the earth,

surely this applies?

https://en.wikipedia.org/wiki/Gravitational_acceleration

The PE is just height x mass x G.

Mass and G stay constant, the centre of mass has lowered therefore the height has lowered.

You mean g.

Technically (sigh), g does decrease with altitude, so a 1 metre drop from 2 metres ASL to 1 metre ASL has slllllightly less PE than a 1 metre drop from 1 metre ASL to sea level, but we are talking about sixth order effects here…

dv said:

sibeen said:

Boris said:

surely this applies?

https://en.wikipedia.org/wiki/Gravitational_acceleration

The PE is just height x mass x G.

Mass and G stay constant, the centre of mass has lowered therefore the height has lowered.

You mean g.

Technically (sigh), g does decrease with altitude, so a 1 metre drop from 2 metres ASL to 1 metre ASL has slllllightly less PE than a 1 metre drop from 1 metre ASL to sea level, but we are talking about sixth order effects here…

yes, that is why i said previously that it was insignificant.

:-)

dv said:

sibeen said:

Boris said:

surely this applies?

https://en.wikipedia.org/wiki/Gravitational_acceleration

The PE is just height x mass x G.

Mass and G stay constant, the centre of mass has lowered therefore the height has lowered.

You mean g.

Technically (sigh), g does decrease with altitude, so a 1 metre drop from 2 metres ASL to 1 metre ASL has slllllightly less PE than a 1 metre drop from 1 metre ASL to sea level, but we are talking about sixth order effects here…

Sorry, I meant g. As far as I can tell PWM’s argument is that the centre of mass of the driver has moved lower as some of the mass is contained in the ‘arms’ of the device. If the CoM has moved lower so has the PE.

Who needs a physics avatar?

I’m not needed here, dv has it all correct.

mollwollfumble said:

Who needs a physics avatar?

I’m not needed here, dv has it all correct.

we don’t because i’m here as well.

:-)

mollwollfumble said:

Who needs a physics avatar?

I’m not needed here, dv has it all correct.

I assume this is all sorted it now.

So I’ll just comment that it’s engineering, not physics.

Peak Warming Man said:

Boris said:

Peak Warming Man said:

The cannons CoM is lower than the CoM of the block and therefore it has less potential energy than the block.

90cm over 6371km isn’t going to make much difference.

Doesn’t matter what the units are and the 90 is just happenstance and is for nothing more than to show the lifts are the same.

The lifts are the same but that diagram seems to show the com falls twice as far in the block pile driver, does this have no significance?

AwesomeO said:

Peak Warming Man said:

Boris said:

90cm over 6371km isn’t going to make much difference.

Doesn’t matter what the units are and the 90 is just happenstance and is for nothing more than to show the lifts are the same.

The lifts are the same but that diagram seems to show the com falls twice as far in the block pile driver, does this have no significance?

How can the CoM fall twice as far. If the thing is lifted x then it will fall x.

The Rev Dodgson said:

AwesomeO said:

Peak Warming Man said:

Doesn’t matter what the units are and the 90 is just happenstance and is for nothing more than to show the lifts are the same.

The lifts are the same but that diagram seems to show the com falls twice as far in the block pile driver, does this have no significance?

How can the CoM fall twice as far. If the thing is lifted x then it will fall x.

personally i don’t think the CoM is relevant.

Boris said:

The Rev Dodgson said:

AwesomeO said:

The lifts are the same but that diagram seems to show the com falls twice as far in the block pile driver, does this have no significance?

How can the CoM fall twice as far. If the thing is lifted x then it will fall x.

personally i don’t think the CoM is relevant.

Yes and no.

It is the change in elevation of the CoM which governs the amount of potential energy converted to dynamic, but as pile drivers fall vertically in a straight line without rotation, you can choose any convenient reference point, such as the impact face.

The Rev Dodgson said:

Boris said:

The Rev Dodgson said:

How can the CoM fall twice as far. If the thing is lifted x then it will fall x.

personally i don’t think the CoM is relevant.

Yes and no.

It is the change in elevation of the CoM which governs the amount of potential energy converted to dynamic, but as pile drivers fall vertically in a straight line without rotation, you can choose any convenient reference point, such as the impact face.

and as the CoM in both cases is raised by the same amount, though not to the same height above the earth, then as you say there is no difference. therefore in this case the CoM is not relevant. surely?

Boris said:

The Rev Dodgson said:

Boris said:

personally i don’t think the CoM is relevant.

Yes and no.

It is the change in elevation of the CoM which governs the amount of potential energy converted to dynamic, but as pile drivers fall vertically in a straight line without rotation, you can choose any convenient reference point, such as the impact face.

and as the CoM in both cases is raised by the same amount, though not to the same height above the earth, then as you say there is no difference. therefore in this case the CoM is not relevant. surely?

Yeah, that’s the no bit.

The Rev Dodgson said:

Boris said:

The Rev Dodgson said:

Yes and no.

It is the change in elevation of the CoM which governs the amount of potential energy converted to dynamic, but as pile drivers fall vertically in a straight line without rotation, you can choose any convenient reference point, such as the impact face.

and as the CoM in both cases is raised by the same amount, though not to the same height above the earth, then as you say there is no difference. therefore in this case the CoM is not relevant. surely?

Yeah, that’s the no bit.

jolly good. i like things plain and simple. except for cake.