How can the action and reaction force be same.? And if so then how the colliding objects could further move as there net force is Zero. Since F1 = - F2, that means that the force act on both sides and as there magnitude is same then undoubtedly there is no such net or derived force for which one could move further.
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This is Newtons 3rd law: When body A exerts a force on body B, then body B will exert an equal but opposite force on body A.
The important thing to realise is that these forces act on different objects. As such, they cannot cancel each other out - unless it is the case of a contact force such as a book resting on a table.
Take a horse and cart for example. The horse exerts a force on the cart, and the cart exerts this force back. However, the horse also exerts a force on the ground, which is why the system does not remain at rest. If the horse and cart were in space, then you would be right - they would not move. However, it is important to realise that there are other forces involved.
Noah P
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Well sir 2nd half of my question is clear. Now sir tell me how the action and reaction forces are same?look according to ur mentions Newton's 3rd law this is applicable for the following situation. I am standing on a park . And a ball hitted me with 5N. Then though I was still and didn't do anything then why that ball would feel the same force,5N? – ffahim Aug 24 '16 at 11:59
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1Because as it hits you, your face resists the motion of the ball, exerting a force back on the ball. – Noah P Aug 24 '16 at 12:01
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1You do act upon the ball just by being present – Noah P Aug 24 '16 at 12:02
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Sir I also understood but how it's same magnitude of force? – ffahim Aug 24 '16 at 12:05
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1You have to assume that newtons second law and the conservation of momentum are true. Then: – Noah P Aug 24 '16 at 12:10
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1$F=\frac{dp}{dt}$, where $p$ is the momentum of the object – Noah P Aug 24 '16 at 12:10
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1If the objects exert forces $F_a$ and $F_b$, and they each have momentum $p_a$ and $p_b$, momentum conservation would give: – Noah P Aug 24 '16 at 12:11
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1$0=\frac{dp}{dt}=\frac{dp_a}{dt} + \frac{dp_b}{dt} = F_a + F_b$ – Noah P Aug 24 '16 at 12:12
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1Then, $F_a=-F_b $ – Noah P Aug 24 '16 at 12:13
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Does that make sense? @ffahim – Noah P Aug 24 '16 at 12:13
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1Strictly speaking, none of newtons laws can be proved, only derived and disproven, but they do all fit with experimental observation – Noah P Aug 24 '16 at 12:14
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Let us continue this discussion in chat. – ffahim Aug 24 '16 at 13:00