force = mass x acceleration

[spunnery]

If Hercules overcomes the static friction, then in case two, you will help him, even if it is a little tiny bit. Again, you can accelerate this 10 ton block in space. It may not be by a lot, just like your help compared to Hercules' will not be a lot, but it will help.

 

Let me create a small example then.

 

Let's say the maximum friction force is 1 million N. You can push with a force of 50 N. Hercules can push with a force of 1.5 million N.

 

You push the block yourself. 50 is not greater than the maximum friction force, so the friction force in this case is 50 N back. Zero net force.

 

Hercules pushs the block himself. 1.5 million is greater than the maximum friction, friction can only counteract with 1 million N. The net result? 0.5 million N in the direction Hercules is pushing.

 

You both push together at the same time. 1,500,050 N is greater than the maximum friction. The net result? 500,050 N in the direction you both are pushing.

 

Your meager contribution compared to Hercules is small, but it is there. And the net force that results is different than just Hercules himself.

Let us get out of the confusion of static friction and all.B'cause it is propotionate to applied force. Instead Of pushing,we will lift the stone.

Say ,we have to lift up a stone, which is exerting a downward force of 200 N(due to gravity) . I am only applying a force of 100 N to lift it. So the stone will remain where it is.

Now you will say the net force acting on the stone is zero.

What i have to say is that,the net force acting on the stone is 100N downwards.

[insane_alien]

you would need ti exhert a force of 200N to keep it there. if your not then its going to fall down.

[spunnery]

you would need ti exhert a force of 200N to keep it there. if your not then its going to fall down.

consider body is resting on ground

[Klaynos]

consider body is resting on ground

 

But you've lifted it up.

 

If you where holding it up with 100N it would accelerate downwards at about 5m/s/s

 

I still hope you are a single person(please don't use plural-and don't think always the rest of world is supporting you).

Let me discuss with you some fundamentals.

Force = mass x acceleration .

Does it means if there is no acceleration means no net force?

 

One other quick point I'd like to make is.

 

[math] F= \frac {dp} {dt}[/math]

 

F=ma is an approximation for when the mass of an object is not changing. So if an objects mass is staying the same, and is not accelerating, there is NO FORCE!

[Bignose]

Again, the stone sitting on the ground has two forces on it: gravity and the force of the ground on the stone. If gravity is 200 N, and the stone is not moving (not sinking onto the ground, not sliding around, etc.), the force of the ground on the stone is also 200 N.

 

Now, you come along and try to lift the stone with 100 N of force. Now there are three forces: 200N of gravity downward, 100N of lifting by you upward, and the the force of the ground on the stone still. Your lifting force was insufficient to lift the stone off the ground, so the ground supplies the remaining force, in this case 100N. Again, the forces sum to zero and there is no movement. No net force, no acceleration.

 

Just to run the gamut of all examples here, say instead lifting the force, you pushed down on the block. Now there is a total of 300 N of downward force, gravity plus your force. In this case, the force supplied by ground to the block becomes 300 N. Again, the net forces sum to zero, which corresponds with the no movement.

 

Finally, if the stone was being held up by someone or something else and you are handed it, but you can only lift 100 N, there is still 100 N of force acting downward. That some is going to move toward the ground, with you in the way, probably hurting you. I am sure you have experienced this when someone has tried to pass you something too heavy for you.

 

Look, I need to state this again, and it is not a personal attack, I am not trying to insult you, I am trying to help make these ideas clearer. But, have you studied physics from a textbook at all? These are pretty basic issues and are covered in the first chapters of any physics text. There will be lots of discussion about this, and the course of study is probably more coherent and collected and directed than questions bouncing back and forth on an Internet forum. I would strongly urge you to go to your local library and check out an Introduction of Physics book and read the first few chapters. This forum will be happy to answer questions you have about the material. But, if you are trying to build this all up on your own, please sit up on the shoulders of the giants who have already done all that building up. Take advantage of the fact that you do not have to start from scratch. Learn from the people who have studied physics thouroughly, who have written some very good texts on the subject, learn from the masters. Like I said above, the system in place today is extremely successful. If you study it, I think you will find that a lot this confusion you have will be cleared up.

 

Like I said, this forum will help answer any questions you have on the material. I'll even extend this offer: you can PM me personally and I will answer any questions you have. But you shouldn't have to struggle to recreate the entire system when the system in place is really good and there are many really good texts that describe this system. So, do yourself the favor of finding a good book, preferably on with a study guide or answer guide or answers printed in the back so you can try some of the problems and see if you understand the material, and read it.

[spunnery]

Just to run the gamut of all examples here, say instead lifting the force, you pushed down on the block. Now there is a total of 300 N of downward force, gravity plus your force. In this case, the force supplied by ground to the block becomes 300 N. Again, the net forces sum to zero, which corresponds with the no movement.

 

 

.

I agree that I am always out of syllabus(I am not trying to put up a new theory on the subject-but to view it from a different angle-may be i am not good enough in expaining my thoughts or you are afraid to go off track).In the above case I will explain My view.A total downward force of 300N is acting downwards,but the ground is not allowing the block to move in the direction of force, by exerting an equal and opposite force.The real problem comes when you try to lift it .You have to apply a force more than 300N ,in the opposite direction to lift the block.which also means that block is still exerting a force of 300 N downwards.

So what i mean is ,it is not always necesssary that a force will create a displacement(displacement can be nullified by an equal and opposite force).Nobody can deny that a downward force is always acting on the mentioned block,otherwise you could have lift it up with a 0.00001 N force.

 

Sorry ,I was not able to get your personel ID.Otherwise i would not have put this subject running on again in this forumn ,to make other people getting Bored.

[Phi for All]

Sorry ,I was not able to get your personel ID.Otherwise i would not have put this subject running on again in this forumn ,to make other people getting Bored.

You don't need a personal ID. Click on a member's name (Bignose invited you to send him a message) at the top left of any of their posts and you will get a menu allowing you to send a Private Message. Type it out like an email and you can send Bignose a message that won't be seen by anyone else.

[spunnery]

You don't need a personal ID. Click on a member's name (Bignose invited you to send him a message) at the top left of any of their posts and you will get a menu allowing you to send a Private Message. Type it out like an email and you can send Bignose a message that won't be seen by anyone else.

Thank you