The Physics of Straws
Straws, how complicated can they be? Most people have a few misconceptions about how straws work, but just like everything else - the answer lies with physics.
Upon placing the straw in a regular cup of water, the pressures inside and outside of the straw are equal! You can see this by noticing that the level of the water and in the glass are the same - both reach the same height of the straw.
When you suck on the straw, you are effectively decreasing the pressure in your mouth - and this lowers the pressure at the top of the straw. As soon as this happens, the force of the atmosphere pushing on the water in the glass is higher than the force of the gases inside the straw. Since pressure acts from high to low, the atmosphere forces the liquid water up the straw. In essence, you are not sucking the water into your mouth, but the atmosphere is pushing it!
Explain this to your friends the next time you’re out to eat - then write down a few bogus equations and they’ll think you’re a genius.