Question on conservation of momentum

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Discussion Overview

The discussion revolves around the concept of conservation of momentum, particularly in the context of measuring weight on a scale during a jump and the outcomes of collisions between two balls. Participants explore the relationship between force, acceleration, and weight measurement, as well as the conditions affecting the velocities of colliding objects.

Discussion Character

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

Main Points Raised

  • One participant suggests that the increased weight measured on a scale when jumping is related to conservation of momentum, but seeks clarification on the concept.
  • Another participant explains that the higher reading on the scale is due to the force required to decelerate the body and counteract gravity, indicating that the scale measures both deceleration and gravitational force.
  • A participant questions the initial explanation, seeking confirmation about the scale's reading being influenced by the need to provide force for deceleration in addition to gravity.
  • It is noted that the scale measures "apparent weight" when accelerating, contrasting it with "gravitational weight," which only accounts for gravitational force.
  • Regarding the collision of two balls, it is mentioned that the material of the balls affects energy loss during the collision, and that under ideal conditions, velocities after a collision can be calculated.

Areas of Agreement / Disagreement

Participants generally agree on the relationship between force, deceleration, and the scale's reading, but there is some confusion regarding the initial explanations. The discussion on the collision of balls remains more open-ended, with considerations about material properties and energy loss not fully resolved.

Contextual Notes

There are assumptions about the nature of the collision (elastic vs. inelastic) and the definitions of weight being discussed, which may affect the conclusions drawn by participants.

Who May Find This Useful

Individuals interested in physics concepts related to momentum, force, and collisions, as well as those exploring practical applications of these principles in everyday scenarios.

rishch
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When you jump on a weighing scale the instant that you hit you're weight is higher than it would be if you were to gently step on on.Can someone give me a proper answer? I think its somehow related to conservation of momentum but i can't think of a proper answer.

Also,suppose you two balls and you know the mass and the velocity of both and then they both collide then is there any way of knowing there velocities after the collision?
 
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The force on the weight from your body is higher initially, because your body decelerates to zero speed. The weight measures the force of deceleration + gravity, and shows higher value till center of mass of the system has stopped, and deceleration has ceased.

To second: Energy is preserved, kinetic energy is constant, Forces are equal in contact
 
1> Is this right-the scale shows more because the scale must provide the force to decelerate your body and also to negate the effect of gravity.
2>I didn't understand your answer.
 
The scale measures the force of gravity pulling your body down towards the Earth. If you are falling onto it then there is more force against the scale than if you were just standing on it. This is called "apparent weight" and is the weight measured if you were accelerating in something such as an elevator. This contrasts with a purely "gravitational weight" which is only measured as the force of gravity on your mass.

To answer your 2nd question you would need to know what the balls were made of. Two beach balls would lose much more energy from the collision than two billiard balls would since the beach balls deform much more and have lots of air.

Assuming a "perfect" elastic collision yes, you could calculate the velocities and other properties of the balls after the collision.
 
rishch said:
1> Is this right-the scale shows more because the scale must provide the force to decelerate your body and also to negate the effect of gravity.
Yes.
 

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