When I reheat last nights curry in a microwave and cover it in clingfilm, the moment I take it out, the clingfilm tightly covers all the crevices and projections of the curry's surface. It is as if there is a vacuum inside. How can this be? Surly nothing has left the covered bowl.

P.S. while the curry in in the microwave the water evapourates and causes the clingfilm to bulge, but when I take it out and the water condenses, there is less pressure inside than before I heated it.

When in the car with my daughter, we noticed that wiht only one window open, travelling at about 40mph+, there was a sort of pulsing noise in the car, sometimes quite unpleasant on the ears.  Usually opening another window stops it, especially if on the opposite side of the car.  My daughter sits in the back, but the same effect happens whether it is her window or mine.  I guess this must be some sort of pressure wave, but we wondered what caused it.

I live in HCMC, Vietnam and two days ago I inflated the tyres on the pushchair to approx 30psi at about 28 degrees clecius. The pushchair is stored in a room around 24 degrees and has been in and out since then.

Today I took the pushchair to the mall (the building is approx 100m tall) in the morning where it was about 32 degress outside and the air conditioning was just turning on inside. We went down two flights of stairs to the basement. We were there about 30 minutes when there was a small pop. The tyre had increased in size and had popped the rim. The other two tyres had also increased in size. Less than two minutes later there was a large bang and the inner tube of the tyre had exploded. I managed to release the pressure on the other two tyres before the same happened to them.

I live in Vietnam and two days ago the tyres on our pushchair were inflated to approx 30psi at around 28 degrees celcius. The pushchair was stored in my son's room at approx 24 degrees and it had been used outside during that time where temperatures would have been over 30 degrees.

Today I took the pushchair to the mall. Went down two flights of stairs into the basement level. I had been there about 30 minutes when there was a small pop, the tyre had increased in size and had popped the rim. I turned the pushchair around and saw the other two tyres had also increased in size. Less than two minutes later there was a large bang and the inner tube had blown. I managed to release the pressure in the other tyres before they exploded too.

If water could be pressurised, how low would the sea level be due to the pressurising weight of the overlying water?

A small spherical projectile made of glass, about 1/4 inch in diameter, would be too influenced by wind to much to go, consistantly, the farthest.  On the opposite hand, a larger spherical projectile made of glass, say 6 inches in diameter, would not be affected by the wind, but may be too heavy and have too much mass to travel to far..  Say the pressure was 10 psi for all sizes of projectiles, what size would the projectile be for optimum distance?

I hope that the changes in the description and the question clarify some things.

I've been dropping squash balls at different temperatures from a constant height of 1m, and measuring the height they bounce up to. I understand that as you heat the squash balls, air molecules inside the ball (which has negligible increases in mass and volume) bounce again each other and the inside of the ball more often and harder, leading to more air pressure in the ball, and thus a higher bounce. Is there any equation that links pressure or temperature with a drop height and bounce height? I've been using Boyle's law, Charles law and the pressure law to find pressure, and there are existing formulae for volumes, of course, but how can I link pressure with bounce? I assume it will involve the coefficient of restitution somewhere, but I'm unsure. Thanks a lot! :)

I've always wondered if, with enough pressure, it were possible to compress water into a solid shape, and have it remain that way.