Sentence Correction

[AsadA969]

Ron,
Is the sentence correct?
Aerodynamics is the study of the forces which act on an object as it moves through the atmosphere.

I think, there is a problem in "which clause". Here, "which" must follow COMMA(,).
Actually, I wanna have a detailed explanation with example why this sentence is not correct (if this sentence is incorrect) and the basic rules of "which" in details.
Anyway, if I wanna correct this sentence by keeping the SAME meaning (without putting the COMMA), how many changes may come in the actual sentence?. I mean, how many sentences I can write without putting the COMMA but meaning will implies WITH COMMA? Could you please give me a solution?
Thanks.

[RonPurewal]

Also, this:

Anyway, if I wanna correct this sentence by keeping the SAME meaning (without putting the COMMA), how many changes may come in the actual sentence?. I mean, how many sentences I can write without putting the COMMA but meaning will implies WITH COMMA? Could you please give me a solution?
Thanks.

I don't understand what you are asking here. When you post the source of the original sentence, please clarify.
Thanks.

[AsadA969]

Sorry for being late.
Ron,
No need to answer the 2nd part (what you have not understood). I'll be satisfied if you answer the first part.
Thanks.

[RonPurewal]

Writers in the UK (and other non-US English-speaking countries) often use "which" where American writers would use "that". The GMAT won't test this difference, so it's a non-issue.

[RonPurewal]

By the way, you still haven't cited the original source of the sentence. That's necessary for any further discussion to happen.

Thanks.

[AsadA969]

There is no original source of this sentence. I've collected it from a seminar thought by a prestigious teacher in my country (Bangladesh). I think, there should use a comma (,) before which.
I just want to have your suggestion about this sentence regarding comma.
Thanks.

[RonPurewal]

There is no original source of this sentence. I've collected it from a seminar thought by a prestigious teacher in my country (Bangladesh). I think, there should use a comma (,) before which.
I just want to have your suggestion about this sentence regarding comma.
Thanks.

I answered this question in my earlier post, though perhaps not as directly as I could have.

In American writing"”including the writing on GMAT SC"”"that", not "which", would be used here.
In other countries, "which" is often substituted for "that".

[AsadA969]

Thanks Ron.

[RonPurewal]

Sure.