Some calculations in Newton's Third Law

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Discussion Overview

The discussion revolves around the application of Newton's Third Law in two scenarios: a machine pushing an object and the behavior of an apple dropped in a vacuum. Participants explore the implications of forces, accelerations, and rebound heights in these contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant presents a scenario involving a 200 kg object and a 5 kg machine applying a force of 600 N, calculating the accelerations of both the object and the machine.
  • Another participant agrees with the calculations but cautions about the signs of the accelerations, noting they would be in opposite directions.
  • A participant questions the terminology used by another, specifically the word "lunge," seeking clarification on its meaning.
  • Clarification is provided that "lunge" was meant to refer to "rebound," with a focus on the behavior of the apple when dropped.
  • Discussion includes the concept of elasticity, with one participant stating that the rebound height of an object depends on its elasticity, mentioning the coefficient of restitution.
  • A later reply asserts that if there is no energy loss, the initial calculations regarding rebound height would hold true.

Areas of Agreement / Disagreement

Participants generally agree on the calculations related to the forces and accelerations, but there is some uncertainty regarding the terminology and the implications of elasticity on rebound behavior. The discussion remains unresolved regarding the exact nature of the rebound height in practical scenarios.

Contextual Notes

Participants express varying levels of understanding and clarity, particularly regarding terminology and the physical principles involved in rebound dynamics. The discussion does not resolve the complexities of real-world applications of elasticity and energy loss.

Who May Find This Useful

This discussion may be useful for individuals interested in the practical applications of Newton's laws, the concepts of force and acceleration, and the behavior of objects in different physical contexts, particularly in relation to elasticity and rebound dynamics.

ahmed emad
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Hello,
1- IF we have an object has 200 kg and we also have a machine has 5 kg and pushes that object with force of 600 n , in Newton third law it must be another force =-600n then : the acceleration of the object must be 3 m\s^2 and the acceleration of the machine is 120 m\s^2 , Am I wrong??

2- if I am in vacuum and I dropped an apple and the distance between my hand and the floor =5 m , is the apple must lunge with 5 m also?? (I said vacuum because I think that the thing causes apple not lunge at the same distance is the air resistance )

And thank you.
 
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ahmed emad said:
Hello,
1- IF we have an object has 200 kg and we also have a machine has 5 kg and pushes that object with force of 600 n , in Newton third law it must be another force =-600n then : the acceleration of the object must be 3 m\s^2 and the acceleration of the machine is 120 m\s^2 , Am I wrong??
You are essentially correct, but be careful about the signs of the accelerations. They would be in opposite directions, so they would have opposite signs in any coordinate system.
2- if I am in vacuum and I dropped an apple and the distance between my hand and the floor =5 m , is the apple must lunge with 5 m also?? (I said vacuum because I think that the thing causes apple not lunge at the same distance is the air resistance )
I don't understand your use of the word "lunge" here.
 
FactChecker said:
You are essentially correct, but be careful about the signs of the accelerations. They would be in opposite directions, so they would have opposite signs in any coordinate system.I don't understand your use of the word "lunge" here.
sorry I am not talk English extremely ,I am from egypt
I meant Rebound
and thank you
 
Ok. The rebound height would depend on the elasticity of the object. Something with perfect elasticity would bounce back to 5 m (ignoring the reaction motion of the Earth). A real apple would primarily squash instead of bouncing. The coefficient of restitution tells how much the object will bounce. (see https://en.wikipedia.org/wiki/Coefficient_of_restitution )
 
If there's no loss of energy due to rebounding or anything else, then yes, you are correct on both.
 

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