Mass, Inertia and Velocity Question

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    Inertia Mass Velocity
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Discussion Overview

The discussion revolves around the concepts of mass, inertia, and their relationship with velocity, particularly in the context of Newton's laws of motion. Participants explore how force, acceleration, and energy relate to objects moving at different velocities, with references to momentum and the implications of increasing speed.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that as an object's velocity increases, the force required to change its velocity also increases, implying a greater inertia and mass.
  • Another participant counters that, ignoring special relativity, a given force produces the same acceleration regardless of the object's velocity, asserting that mass does not increase with speed.
  • A follow-up question raises the idea that an opposing force needed to change an object's velocity might be greater at higher speeds.
  • Participants discuss the concept that while more energy is required to stop a fast-moving object, this does not imply an increase in mass or inertia, but rather an increase in kinetic energy and momentum.
  • Clarifications are made that the rate of velocity change remains constant for a given force, regardless of the object's speed.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between velocity, inertia, and mass. While some argue that greater energy is needed to stop faster objects, others maintain that mass remains constant and does not increase with speed. The discussion remains unresolved with multiple competing views present.

Contextual Notes

Participants reference concepts such as kinetic energy and momentum without reaching a consensus on the implications of these concepts for mass and inertia at varying speeds.

jason006
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I know that Inertia is an objects resistance to a change in its velocity and Mass is the amount of Inertia which an object posseses so here is my question:

When an object moves at an increasing velocity, won't the amount of force needed to change its velocity increase? Therefore the object has a greater inertia and therefore a greater mass.

Thanks

P.S If this question sounds a bit stupid its because I recently started Grade 11 at school in January and was just introduced to Momentum, Newtons Laws, Impulse and Inertia
 
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jason006 said:
When an object moves at an increasing velocity, won't the amount of force needed to change its velocity increase? Therefore the object has a greater inertia and therefore a greater mass.
No. Forgetting about special relativity for the moment, a given force on an object will produce the same acceleration (the rate of change of velocity) regardless of the object's velocity. Mass doesn't increase with speed.
 
Doc Al said:
No. Forgetting about special relativity for the moment, a given force on an object will produce the same acceleration (the rate of change of velocity) regardless of the object's velocity. Mass doesn't increase with speed.

But what about a force in the opposite direction than that of the force causing the object to accelerate? Wouldnt that opposite force needed to change the objects velocity be greater if the object was moving with a greater velocity
 
jason006 said:
But what about a force in the opposite direction than that of the force causing the object to accelerate? Wouldnt that opposite force needed to change the objects velocity be greater if the object was moving with a greater velocity
No. Why do you think that? Can you give a more specific example of what you mean?

Perhaps you are thinking that it requires more energy to stop a fast moving object than a slower moving object? That's certainly true. But for a given net force, the object's acceleration is the same regardless of its speed.
 
Doc Al said:
No. Why do you think that? Can you give a more specific example of what you mean?

Perhaps you are thinking that it requires more energy to stop a fast moving object than a slower moving object? That's certainly true. But for a given net force, the object's acceleration is the same regardless of its speed.

Yes, so if you so more energy is needed to stop a fast moving object then its inertia would be greater wouldn't it?
 
jason006 said:
Yes, so if you so more energy is needed to stop a fast moving object then its inertia would be greater wouldn't it?

No only its momentum.
 
jason006 said:
Yes, so if you so more energy is needed to stop a fast moving object then its inertia would be greater wouldn't it?
No. It's kinetic energy (and momentum) is greater, not its mass. Since the mass remains the same, a given force will produce a given acceleration. So if something is moving faster, you'll have to exert that force for a longer time to stop it compared to if it were moving slower. But the rate at which the velocity changes will be the same.
 
Doc Al said:
No. It's kinetic energy (and momentum) is greater, not its mass. Since the mass remains the same, a given force will produce a given acceleration. So if something is moving faster, you'll have to exert that force for a longer time to stop it compared to if it were moving slower. But the rate at which the velocity changes will be the same.

oh yes. thanks a lot
 

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