Sentence Correction

I got a question on this subject.

From Sahil's notes:

7)Singular verb or plural: When the subject is plural use a plural verb.
e.g. In laws of motion, there is a condition and its converse regarding bodies at rest and bodies in motion. – This is incorrect.

The correct sentence would be : In laws of motion, there are a condition and its converse regarding bodies at rest and bodies in motion.

I don't know why but this sounds awkward to me. Is the above example correct?

Could someone please explain this further using other examples?

Thanks
skimo [/quote]

This sounds wrong because the last word of the plural subject, 'laws of motion', does not end with an 's' and so it doesn't sound plural.

This is a common trick in the GMAT.

Other examples of plural subjects that may sound singular could be 'cars which run on natural gas', or 'students of the GMAT' etc.

They also use the reverse trick of picking a singular subject which sounds plural. For example 'the United States' is singular even through it sounds plural.

See our sentence correction tutorial for more help with this.

thanks!

Original sentence: In laws of motion, there is a condition and its converse regarding bodies at rest and bodies in motion. - This is incorrect.

The correct sentence would be : In laws of motion, there are a condition and its converse regarding bodies at rest and bodies in motion.

I agree . the original sentence is incorrect. But in the correct sentence i found some flaws.can some please explain why isnt the second statement wrong?

Not quite sure whether the highlighted words are correct grammatically.