# The Naked Scientists Forum

### Author Topic: How do balanced forces cause motion according to Newton's laws?  (Read 905 times)

#### Dr Amrutha

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##### How do balanced forces cause motion according to Newton's laws?
« on: 21/04/2016 17:20:59 »
If you imagine a situation of tug of war played by two teams exerting equal forces,in that case,no team experiences a motion,that is no single team gets pushed out of the border line (I assume you know the tug of war game)
If that is the case here,then how does Newton actually say that balanced forces cause motion ? I mean doesn't that sound instinctually wrong ?

#### evan_au

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##### Re: How do balanced forces cause motion according to Newton's laws?
« Reply #1 on: 21/04/2016 19:40:24 »
Quote from: Dr Amrutha
balanced forces
Equal and opposite forces means zero net force.

Quote
how does Newton actually say that balanced forces cause motion ?
If there is no net force, an already-moving body will continue to move. If it is not already moving, it will continue to not move.

Quote from: Newton's First law
When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force
See: https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion

However, in a game of tug-of-war, the applied forces are not steady and balanced, but are varying dynamically, so one team gains a temporary advantage, and the other team collapses.

#### Dr Amrutha

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##### Re: How do balanced forces cause motion according to Newton's laws?
« Reply #2 on: 22/04/2016 06:15:36 »
What if the applied forces by each team in the tug of war game was equal ? In that case,none of the team wins or collapses,right ? What I can't understand is if the forces are equally exerted on an object,then they are still said to be in motion as said by Newton.That can't be true in tug of war game,can it ?

#### Colin2B

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##### Re: How do balanced forces cause motion according to Newton's laws?
« Reply #3 on: 22/04/2016 09:26:30 »
What if the applied forces by each team in the tug of war game was equal ? In that case,none of the team wins or collapses,right ?
Yes, that's what Evan said

What I can't understand is if the forces are equally exerted on an object,then they are still said to be in motion as said by Newton.
Where does it say that?
Forces don't have to be in motion. Static forces still exert a force. If the forces are balanced there is no motion, if they are unbalanced there is motion.

#### agyejy

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##### Re: How do balanced forces cause motion according to Newton's laws?
« Reply #4 on: 22/04/2016 11:37:39 »
What I can't understand is if the forces are equally exerted on an object,then they are still said to be in motion as said by Newton.
Where does it say that?
Forces don't have to be in motion. Static forces still exert a force. If the forces are balanced there is no motion, if they are unbalanced there is motion.

Mild correction to hopefully avoid confusion. If the forces are balanced there is no change in motion, it they are unbalanced there is a change in the motion. That is to say unbalanced forces cause an object to speed up, slow down or change direction. Balanced forces can absolutely be acting on an object that is in motion relative to you and said object will remain in that exact state of relative motion as long as the forces are balanced. Normally I wouldn't be so nitpicky but this specific point seems to be the origin of the misunderstanding.

#### Colin2B

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##### Re: How do balanced forces cause motion according to Newton's laws?
« Reply #5 on: 22/04/2016 13:18:48 »
Mild correction to hopefully avoid confusion.
Thanks, that's what comes of posting in a hurry.

Somewhat confused by the confusion as I thought Evan covered it very clearly.

#### The Naked Scientists Forum

##### Re: How do balanced forces cause motion according to Newton's laws?
« Reply #5 on: 22/04/2016 13:18:48 »