Need help with finding measurements.

[mrmusterd]

I need to know how to measure certain things, they include:

Measuring the amount of hairspray that comes out of a hairspray container in 5 seconds, how can I measure how much this is?

Measuring the capacity of a x" long piece of PVC that is x" in diameter

Is there a way to measure pressure besides a PSI gauge?

How do explosions force projectiles out of a barrel?

Thanks.