Straw Cup
Straw Cup
How do bubbles form when you blow from the straw into the cup?
When you blow from the straw into a glass of water. Usually buuble form. But how are they formed?
You Are forcing air from your lungs into the water through the straw. Even if you provide a continuous and steady supply of air, you will see that you will not get a huge air bubble but instead you will get many small air bubbles. How does this happen?
As air reaches the bottom of the straw and starts coming out of it will immediately experience buoyancy, which pushes the air upwards. This can be explained by Archimedes’s Principle but this is not your question so let’s don’t spend time here. Water is surrounding the air as it peeks through the bottom end of the straw. The surface tension in the interface water-air keeps (to some degree) the air mass together as the bubble forms in the opening of the straw. There will be a time where the buoyancy experienced by the mass of air being pumped is greater than the surface tension trying to keep this volume of air together and at this time the air mass will split and break: one part will move upwards and the other part will still remain in the opening of the straw, forming another bubble.
Based on this explanation, you could infer that if a liquid has less surface tension than other then the size of the bubbles as they break up from the bottom of the straw should be smaller in size than the bubbles formed in a liquid with a higher surface tension. You could try to compare the size of the bubbles in water and the bubbles in water mixed with detergent (which decreases surface tension in water). Might be hard to see the difference though.
Why do bubbles have a spherical shape? Because the air inside the bubble is pushing in all directions with the same magnitude and this produces a sphere. Additionally the size of the bubble will increase as it moves upwards because there is less hydrostatic pressure and this allows the expansion of the air inside the bubble. This is easy to prove if you watch on TV people diving hopefully showing the bubbles as they move up. This is also the reason why divers are told the first day of training that they should never keep air inside their lungs and ascend. This air inside the lungs will expand and could burst the diver’s lungs. So remember, a certain volume of air underwater will expand its volume as it moves up to surface. We can’t see much difference in a glass of water as it is not deep enough.
At what age can a baby have a cup with a straw?
...and is there anything bad caused by using a straw often?
Whenever your child learns how to suck out of a straw you can start giving a cup with a straw. My son learned how to use a straw at about 19 months old and now he loves to drink out of a cup with a straw.
Cleaning a Straw Cup
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 Solo Cup Company Diner Straw Dispenser Stainless Chute FAUX Wood Grain  US $22.75
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 TUPPERWARE Impressions 16oz DRIPLESS Straw Seals TUMBLERS Drink cups New US $24.96
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 2 Brand New Star Wars Clone Wars Cup w Straw w Candy US $4.50
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 Tigger straw cup with screw on head lid US $.99
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 VALENTINES DAY FLORIDA MARLINS CUP w lidstraw1998 topps baseball CARDSCANDY US $4.99
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 Tupperware New 32 oz Large Beverage Tumbler Cup Dripless Straw Seal Green Rare US $17.99
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 Old DISNEY Mickey Mouse juice cup w straw US $2.95
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 2 Barnies Coffee and Tea Company Red Plastic Travel Drink Cups Straw Opening US $19.99
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 Large Tupperware Moms Rule Cup With Straw hole Lid White with Red US $5.99
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 New Starbucks Reusable Green Grande Straw for 16oz Iced Tumbler To Go Cups US $2.50
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 New Starbucks Venti Green Reusable Straw for 20oz 24oz Iced Tumbler To Go Cups US $2.50
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 Disneyland 1998 Lmtd ED grand opening TOMORROWLAND novelty straw cup VGC US $4.99
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 Tupperware New RED Popsicle Insulated Tumbler Cup DripLess Straw White Seal US $20.49
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 Tupperware NEW IMPRESSIONS PURPLE 16 Ounce Tumblers CUPS Drip Less Straw Seals US $26.99
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 2011 Holiday Starbucks Clear To Go Tumbler CupStraw New Logo Quick Ship US $18.99
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 Vtg Mickey Mouse Disney Old Sippy Straw Cup US $6.00
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 Tupperware New RARE Aqua Blue Insulated Tumbler Cup DripLess Straw White Seal US $19.99
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 Starbucks Blue Cup Mug W Straw US $7.00
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 Corvette Cup W Straw US $.99
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 Coffee Cup with Straw and Creamer Disney Pin US $.99
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 Disney Lilo Stitch Childrens Cup w Straw Lid NEW US $3.99
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 THE ROCK WWE LEGENDS RARE SERIES 3 7 11 STRAW FIGURE AND CUP UNUSED RARE US $19.11
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 Closeout Auction 1 LUAU PARTY PINEAPPLE SIPPER STRAW CUP BOTTLE 20oz US $3.83
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 Tupperware New 32 oz Large Beverage Tumbler Cup Dripless Straw Seal Teal Rare US $17.99
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 Tupperware New Red Popsicle Insulated Cup Dripless Straw White Seal Free Straw US $22.98
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 Tupperware Coffee Drink MUG Juice CUPS Toddlers Dripless Straw Seals NEW RED US $15.39
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 STARBUCKS SET OF 2 HOLIDAY WINTER 12 OZ COLD CUPS TUMBLERS WITH CHANGING STRAW US $27.99
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 ARGENTINA MATE GOURD CUP KIT STRAW YERBA MATE FREE US $10.05
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 Disney Store Pooh Tigger 8 oz Snowglobe Tumbler Sippy Cup With Straw NEW US $6.50
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 New Reusable Green Grande Straw for Reusable 16oz Iced Tumbler To Go Cups US $2.50
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 Winnie the pooh cup with straw US $4.00
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 Silver 800 CUP GOURD MATE BOMBILLA STRAW SET 18K Gold tip on Bombilla US $132.49
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 Tupperware Insulated Dripless Straw Seal Travel Cup Drink TUMBLER 24 oz Red NEW US $16.39
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 New Yo Gabba Gabba Brobee Fun Float Straw Cup Boy Girl Toddler Kid Safe BPA FREE US $6.95
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 STARBUCKS Coffee Grande To Go Tumbler Cup XMAS Candy Cane Straw Free Priority SH US $21.95
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 DISNEY MINNIE MICKEY HOLIDAY PLASTIC CUP WITH RED STRAW US $4.99
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 12 20 OZ PLASTIC DRINKING GLASSES LIDSTRAW CUP TUMBLER US $22.67
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 STARBUCKS Brand New 20oz Cup With Lid Built In Straw For Home Or Office US $12.99
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 12 20 OZ PLASTIC DRINKING GLASSES LIDSTRAW CUP PEARLIZED TUMBLERS MFG USA US $29.61
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 toysippy cupstraw cup with name boygirlbaby NIP US $5.00
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 toysippy cupstraw cup with name boygirlbaby NIP US $5.00
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 DISNEY PINS ☠ New Orleans Square Mint Julep Bar Disneyland Cup Glass Straw NOS US $.99
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 1000 Dart Foam Cup Lids tear tab straw slot 16 oz 20oz W16J5 W20J16 US $14.99
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 NEW 1992 OAKLAND ATHLETICS 24oz w Cup Straw Belt Clip US $6.99
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 NEW 1990 SAN DIEGO PADRES 24oz w Cup Straw Belt Clip US $5.99
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 NEW 1990 ATLANTA BRAVES PLASTIC 9 tall DRINKING CUP straw belt clipetc US $9.99
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 Vtg Kelloggs Corn Flakes BOY Cup Mug w Straw Hat EUC US $4.99
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