Physics question(s)

[tinfoilhat 11]

Simple one for those that know, I don't, so please dumb down the answer, I'm not an eager under graduate I'm a inquisitive dullard.

 

Right, imagine I have a metal pole 3 metres high (weight 5kg), stood upright with the bottom end attached to 30cm square base (the pivot point I suppose). If that is pushed over what is the force of the top end of the pole when it hits the floor and how is that translated into real terms - ie will it break an apple, a cardboard box or a rock?

 

Is there a formula (a very very very simple formula) where I can upscale length of pole and/or size of base to see if say a 4m pole would create twice as much force, or more, or less. Is there a rough guide where I can see X amount of force will do Y amount of damage in real terms?

 

Thanks in advance!

[savagestone 10]

, i need feet and inches, thanks,

 

---------- Post added 09-08-2016 at 20:43 ----------

 

i need feet and inches thanks,

 

---------- Post added 09-08-2016 at 20:44 ----------

 

and pounds and ounces

[tinfoilhat 11]

10ft pole, 11lb base.

[*_ash_* 88]

Would the weight of the base be required to work this out (if it's attached to it)?

 

Just guessing I have no idea. I had to double check Alcoblog didn't post this

[tinfoilhat 11]

Would the weight of the base be required to work this out (if it's attached to it)?

 

Just guessing I have no idea. I had to double check Alcoblog didn't post this

 

I'm not sure. It will affect the amount of force required to get it to its tipping point but after that I'm not sure if it affects the force past the tipping point.

 

Weight of the base would be about 10kg (at a guess).

[Santo 10]

Simple one for those that know, I don't, so please dumb down the answer, I'm not an eager under graduate I'm a inquisitive dullard.

 

Right, imagine I have a metal pole 3 metres high (weight 5kg), stood upright with the bottom end attached to 30cm square base (the pivot point I suppose). If that is pushed over what is the force of the top end of the pole when it hits the floor and how is that translated into real terms - ie will it break an apple, a cardboard box or a rock?

 

Is there a formula (a very very very simple formula) where I can upscale length of pole and/or size of base to see if say a 4m pole would create twice as much force, or more, or less. Is there a rough guide where I can see X amount of force will do Y amount of damage in real terms?

 

Thanks in advance!

 

Can we assume the pole is tilted and topples under the effect of gravity alone?

 

Otherwise it would depend on how hard you push it over.

[Alcoblog 10]

I'd imagine it'd be pretty easy to 'break' an apple merely by chucking the rock at it … in fact the pole could potentially get in the way of a clear lob. Eating apples are softer than cooking ones though if that's any help.

Quite where the cardboard box comes into the equation is anyone's guess though, unless it's to put all the mess in after?

[tinfoilhat 11]

Can we assume the pole is tilted and topples under the effect of gravity alone?

 

Otherwise it would depend on how hard you push it over.

 

Nudged over with minimum force until it reaches its "natural (?)" tipping point as opposed to, for example, driving a car in to it doing 60mph.

 

So yes, what you said.

 

(Should have put that in the OP).

[Santo 10]

Nudged over with minimum force until it reaches its "natural (?)" tipping point as opposed to, for example, driving a car in to it doing 60mph.

 

So yes, what you said.

 

(Should have put that in the OP).

 

That makes it easier. Writing the equations on the forum might be difficult.

 

The basic physics would be similar to the domino effect once demonstrated on QI (knocking over the Shard with a feather).

 

You'd only need the expression for n=1.

[Ghozer 112]

It would partly depend on the weight of the base also, and the thickness, as a thicker base..... as that would counter the force as the pole was falling...

 

Also, the surface it's stood on (as grass vs concrete, or even wet vs dry grass etc)

weather conditions, clear sunny day etc....

[Orzel 10]

Is this purely theoretical or practical exercise?

What is base weight?

Are those 3 meters sticking out of base?

 

Too slow, 10kg base

Edited August 9, 2016 by Orzel
too slow

[Santo 10]

It would partly depend on the weight of the base also, and the thickness, as a thicker base..... as that would counter the force as the pole was falling...

 

Also, the surface it's stood on (as grass vs concrete, or even wet vs dry grass etc)

weather conditions, clear sunny day etc....

 

The mass of the base as a ratio to the system as a whole is only relevant to the centre of gravity. Once tipped beyond that it will fall over.

 

Grass vs concrete makes no difference. Neither does weather. A pole wouldn't suffer much air resistance and a 10kg base wouldn't much be affected by breeze.

 

It's not an easy question to answer. If we assume the base is uniform and a regular shape (circular, square, even hexagonal, whatever) and uniform density and the pole is uniform density standing straight up in the middle of the base then the centre of mass will be somewhere along the pole. We need to know where the centre of mass is to determine to angular acceleration when it topples. That is required to calculate the force and answer your question.

 

Take a look at the physics for just the pole by itself, where the centre of mass is half way along the pole. A base complicates things somewhat!

 

http://www.okphysics.com/1-53-rod-falling-from-a-vertical-position/

Edited August 9, 2016 by Santo