Mass, Inertia and Velocity Question

In summary: . so basically if an object is moving faster then the force needed to change its velocity will be greater and the object will have a greater mass.thanks for the clarification.
  • #1
jason006
6
0
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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  • #2
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.
 
  • #3
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
 
  • #4
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.
 
  • #5
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?
 
  • #6
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.
 
  • #7
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.
 
  • #8
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
 

FAQ: Mass, Inertia and Velocity Question

1. What is mass?

Mass is a measure of the amount of matter in an object. It is typically measured in kilograms (kg) and is a fundamental property of an object. The more mass an object has, the greater its inertia and the more force is needed to accelerate it.

2. What is inertia?

Inertia is the tendency of an object to resist changes in its state of motion. It is directly related to an object's mass - the larger the mass, the greater the inertia. This means that more force is needed to accelerate an object with a larger mass compared to an object with a smaller mass.

3. How does velocity affect an object's motion?

Velocity is the rate of change of an object's position with respect to time. An object's velocity can affect its motion in multiple ways. For example, if an object is moving with a constant velocity, it will continue to move at that same speed and direction unless acted upon by an external force. On the other hand, if an object's velocity is changing, its motion will also change accordingly.

4. What is the relationship between mass and velocity?

According to Newton's second law of motion, the force needed to accelerate an object is directly proportional to its mass and its acceleration. This means that as an object's mass increases, the amount of force needed to accelerate it also increases. Additionally, an object's velocity can also be affected by its mass - for the same amount of force, an object with a larger mass will have a lower acceleration compared to an object with a smaller mass.

5. How does an object's mass and velocity affect its kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is directly proportional to both an object's mass and the square of its velocity. This means that an object with a larger mass and/or a higher velocity will have a greater kinetic energy compared to an object with a smaller mass and/or a lower velocity.

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