Question: In the movie, Inception, 2010 film.
EAMES was sitting down, and COBB approached to him. And said, 

> 
> "**You're on.** You've got an hour. Now get us something useful."
> 
> 
> 

I googled it and found this : 

<https://english.stackexchange.com/questions/36434/why-does-youre-on-mean-i-agree>

But, seems it doesn't make sense for this. Right?

I just try to guess and maybe it means "It's your turn." doesn't it?

Could you please give a few examples in order for me to understand quick?

Thank in advance.

Answer: 
In this case, since EAMES already works for COBB, I think the meaning is more along the lines of definition 5 or 5.1 at [oxford dictionary.com's ON definition](http://www.oxforddictionaries.com/definition/english/on?q=on#on) (thanks to MaulikV for the link):

> 
> (Of an actor) on stage; performing.  
> 
> *That's your cue. You're on.* 
> 
> 
> (Of an employee) working; on duty.
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> 

I would lean more toward the "actor giving a performance" definition, as COBB's task is to trick someone into giving away information, but I think both senses are appropriate.
In this context, the meaning of *on* maps to [this definition](http://dictionary.cambridge.org/dictionary/british/on_30):

> 
> **on** (*adverb*) `PERFORMING` performing: *Hurry up with the make-up – I'm on in ten minutes.*
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> 
> 

While this meaning is often used in television, radio, and the stage, it could also be used during a con scam (as in the movie), or even in marketing.

At an expo, for example, one of my associates might be getting ready to demo our product, and I might say:

> 
> Okay, you're on. Look sharp; be confident.
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Or perhaps my daughter is giving a speech:

> 
> You're on tomorrow. Practice one more time, and then get a good night's rest.
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>