I couldn't tell you how many lbs of pressure there would be but as an example...
next time you see a hood off a car and the springs/hinges are still mounted, try to push the hood spring down to the open position.

I say while it's on the car because I don't think you would be able to open the hood hinge in your bare hands while it was off the car.

You could also mount it in a vice.

The point being.....how much pressure?

Quite a bit.

Better yet...remove the sping from the hood hinge and try to stretch the spring.

Frank