What is the Relationship Between Time and Force in Particle Motion?

[Jiman]

I feel that force is also function of time.

 

[PeroK]

The natural forces of gravity and electromagnetism depend on position (inverse square law). If a particle is moving then the force is indirectly a function of time, as it changes position when it moves.

If you have an electric field, say, that is also a function of time, then the force at a given point depends explicilty on time.

 

[Jiman]

This is only true for particle but not for extensive body?

 

[PeroK]

This is only true for particle but not for extensive body?

A body is a collection of particles.

 

[Jiman]

A body is a collection of particles.

Thank you so much!

 

[ZapperZ]

I feel that force is also function of time.

I am sure that you are citing this out of context, which is a nasty thing to do to any author. You should at least make an effort at (i) citing the exact phrase that led you to conclude this and (ii) citing the location of the source, i.e. where in the book did you get this.

Force can be defined as the gradient of the potential energy field, i.e.

F = -∇U

By that alone, I can claim that force depends only on position, since it is a function of the gradient (i.e. d/dx) of the potential energy field.

So how is that not correct in this context?

Zz.

 

[Jiman]

I am sure that you are citing this out of context, which is a nasty thing to do to any author. You should at least make an effort at (i) citing the exact phrase that led you to conclude this and (ii) citing the location of the source, i.e. where in the book did you get this.

Force can be defined as the gradient of the potential energy field, i.e.

F = -∇U

By that alone, I can claim that force depends only on position, since it is a function of the gradient (i.e. d/dx) of the potential energy field.

So how is that not correct in this context?
Thank you for reminding me. I'll correct it.

Zz.

 

[ZapperZ]

Thank you for reminding me. I'll correct it.

You need to learn how to communicate in a clearer manner here. In the 4 posts that you have made in this thread, all of them were one-sentence responses. In this post alone, I've typed more than what you had written, combined!

It is difficult to know what it is really that you are going to "correct". Furthermore, I don't see any indication that you've understood the answer that you were given, since you did not indicate that one way or another.

If you wish that members responding to your questions provide detailed and thoughtful answers, you should at least put in the same level of effort in your questions and posts.

Zz.

 

[Jiman]

You need to learn how to communicate in a clearer manner here. In the 4 posts that you have made in this thread, all of them were one-sentence responses. In this post alone, I've typed more than what you had written, combined!

It is difficult to know what it is really that you are going to "correct". Furthermore, I don't see any indication that you've understood the answer that you were given, since you did not indicate that one way or another.

If you wish that members responding to your questions provide detailed and thoughtful answers, you should at least put in the same level of effort in your questions and posts.

Zz.

Sorry, English is not my native language. I hardly use English in my life. But I can understand what you're replying to.

 

[wrobel]

Sorry, English is not my native language.

PF is tolerable for this. It is one of the reasons I like it

 

[Leo Liu]

"At first glance there seems to be no problem in finding the motion
of a particle if we know the force. Newton’s second law tells us the acceleration,
which we can integrate to find the velocity, and we can then
integrate the velocity to find the position. This sounds simple but there
is a problem: to carry out these calculations we need to know the force
as a function of time, but force is usually known as a function of position
as, for example, the spring force or the gravitational force. The
problem is serious because physicists are generally interested in interactions
between systems, which means knowing how the force varies with
position, not how it varies with time."