Is Weight an External Force in Collision Scenarios?

AI Thread Summary
In collision scenarios, weight is considered an external force when analyzing the momentum of a single object, such as an apple, because it affects the object's velocity. If only the apple's motion is considered, gravity is an external force, and momentum is not conserved. However, when both the apple and the Earth are included in the system, gravity becomes an internal force, allowing for the conservation of momentum. The law of conservation of momentum states that total momentum remains constant unless acted upon by an external force, which in this case is the Earth's gravitational pull. Therefore, weight is indeed an external force in collision contexts.
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In collision, law of conservation of momentum is applied only if no external force is added. Is weight considered as an external force? I think so. Anyone tell me ?

If an apple falls from a tree and hit the earth. Is the weight considered as external force?
Also, when they are in contact and starts to collide, the apple or the Earth is back, in other words, the distance after impact is larger than that when it is at the moment of impact.
However, the Earth would have a force that pulling the apple coming towards it again after impact, and the velocity then is affected from the law of conservation of momentum and thus I consider weight is an external force,isn't it?
Any advice is treasure
 
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I'm not at all sure I understand what you are saying!

What is or is not an external force depends upon what you are considering as part of the "system". If, in a problem involving a moving apple, you are considering only the motion of the apple, then gravity is an "external" force. The momentum of the apple is not conserved. If, in that same problem, you are considering the motion of both the apple and the Earth (rather unusual) then gravity is an "internal" force and momentum (of the earth-apple system) is conserved.
 
Yes, weight is considered an external force in the context of collisions. The law of conservation of momentum states that the total momentum of a closed system remains constant unless acted upon by an external force. In the case of the apple falling from a tree and colliding with the Earth, the Earth's gravitational force (represented by weight) is an external force acting on the system of the apple and the Earth. This force causes a change in the velocity of the apple and the Earth after the collision, and the law of conservation of momentum takes this into account. So, in this scenario, weight would be considered an external force.
 

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