Newton's First Law: expression "inertia must be overcome"

[NinaZara]

According to Newton's 1st Law, starting something new is difficult because inertia must be overcome.

Can somebody please explain to me why we don't use overcame? Is it because overcome is an adjective here?

Thanks

[Yankee]

Hi NinaZara

'Overcame' is used for the simple past tense.

In your sentence, 'overcome' is not used as an adjective. 'Must be overcome' is the passive form of 'must overcome'. In your sentence 'overcome' is a past participle. To build the passive, you need to use a form of 'be' along with the past participle of the verb.

Here is an example of an active sentence and its passive version:

You must write a letter of apology.
A letter of apology must be written.

Amy

[NinaZara]

Thanks Yankee.

Sometimes I wonder whether I think too much or too deep (or I'm just lazy and not think at all ).You make it sounds so easy, why didn't I think of it before?Sigh...

[Yankee]

Hi NinaZara

I have a feeling you were just thinking too much.

As for "easy"... well, I am a native speaker and started teaching ESL courses quite a long time ago. I've been asked similar questions many times in the past.

By the way, I think your niece is adorable. What a nice picture of the two of you.

Amy

[NinaZara]

On behalf of Aisya and myself, thanks again, Amy.