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Because under your thumb, inside the straw, there is now a vacuum which keeps the water in.

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Q: Why do the water in a drinking straw does not drip out when you press the top of the straw with your thumb or finger tip?
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Why does the drinking straw does not drip out when you press the top of the straw with your thumb or finger tip?

Your finger prevents air from entering through the top of the straw. As fluid moves down the straw it leaves a void in it's wake, one that is usually immediately filled by air. By preventing the air from entering the top of the straw, the fluid cannot move downwards because to do so would leave a vacuum space between your finger and the fluid; this "sucks" the fluid back in into place and prevents it from decending down the straw.


Why does a straw hold water if you put your thumb over top of it?

When a thumb is placed over the hole in the top of the straw, it seals the entry way for air. When the straw is pulled out of the water, it is to be noted that a drop or two of water falls out of the bottom but no more falls. This is because when the water droplets fall, this creates more space in the air pocket in the top part of the straw. WIth more space the pressure decrease in the air pocket. In addition, gravity is working on the water inside the straw, but these two forces do not outweigh the force of atmospheric pressure outside, as a result, the water stays within the staw.


Where does the noise come from when clicking your fingers?

Sound is made when air particles vibrate. So when you click your fingers, you're causing the air particles around your finger to vibrate, causing the noise you hear. The noise you hear is actually a mixture of 2 sounds; the sound of your middle finger sliding off your thumb, and also the sound of your middle finger hitting your hand.


How do you pierce a needle into the balloon and not to break the balloon?

...by pinching the balloon between your thumb and index finger and inserting the needle between the compressed rubber of the balloon at that point without letting go of the compressed balloon until you release the needle from the balloon.


Do vacuum tubes did it lead to an increase or decrease in size?

Vacuum tubes vary from thumb size to larger than most people. Integrated circuits or ICs' are the size of you little finger nail. There was nothing worth remembering before vacuum tubes.

Related questions

The water in a drinking straw does not drip out when you press the top of the straw with your thumb or finger tip?

there is no air


Why the water in a drinking straw does not drip out when you press the top of the straw with your thumb of finger tip?

Because under your thumb, inside the straw, there is now a vacuum which keeps the water in.


Why does the drinking straw does not drip out when you press the top of the straw with your thumb or finger tip?

Your finger prevents air from entering through the top of the straw. As fluid moves down the straw it leaves a void in it's wake, one that is usually immediately filled by air. By preventing the air from entering the top of the straw, the fluid cannot move downwards because to do so would leave a vacuum space between your finger and the fluid; this "sucks" the fluid back in into place and prevents it from decending down the straw.


What is the fingerings for D natural on the flute?

Lowest - Left hand - thumb(1st finger), 2nd finger, 3rd finger and 4th finger Right Hand - 2nd finger, 3rd finger and 4th finger (no pinky) Middle - LH - thumb, 3rd finger, 4th finger RH - 2nd finger, 3rd finger and 4th finger (no pinky) Top - LH - thumb, 3rd finger and 4th finger RH - none


Why is thumb finger called thumb?

The thumb is called a thumb instead of a finger because it is smaller than a finger. A thumb also has 2 joints and a finger has 3.


The water in a drinking straw does not drip out when you press te top of the straw with your thumb or finger tip?

It's a matter of air pressure that acts on the water. When the straw is uncovered, there are two forces acting on the water inside. There is gravity, pulling the water down, and air pressure. The pressure is about the same on both ends of the straw, but on the top of the straw, the pressure pushes the water downward, and on the bottom of the straw, the pressure pushes upward. Both of the pressures are the same, so the net force is just the force of gravity pulling the water down and out of the straw. When you cover the top of the straw, you block the air from pushing down on the water. In this case, the only forces on the water are the air pressure pushing up, and gravity pulling down. However, the air pressure is a greater force than gravity, and keeps the water in the straw despite gravity's pull.


Which finger is your forefinger?

Your forefinger is your pointer or index finger. It is the finger next to your thumb.


What does span mean in bowling?

It is the measurement between the thumb and middle finger, thumb and ring finger and middle finger to ring finger.


Which finger is the pointer finger?

its the finger right next to your thumb


Which is index finger?

Finger next to the thumb, i.e. To the immediate right of the thumb on your right hand To the immediate left of the thumb on your left hand


What is the longest finger on your hands?

Everyone thinks that your middle finger is the longest finger on your hand, but according to doctors, the thumb (which is counted as a finger) is the longest. Your thumb does not end at the crease, it ends at the bone close to your wrist. your thumb is the longest finger on your hand!


Is the index finger the middle finger?

No, the index finger is next to the thumb. Then the middle finger. Then the ring finger. Then the little finger, sometimes called pinky. no its the one between the middle finger and the thumb. The one you point it.