Question

A drinking straw 20 cm long and 3.0 mm in diameter stands vertically in a cup of juice 8.0 cm in diameter. A section of straw 6.8 cm long extends above the juice. A child sucks on the straw, and the juice level begins dropping at 2.2 mm/s .

By how much does the pressure in the child's mouth differ from atmospheric pressure?

What is the greatest height above the water surface from which the child could drink, assuming this same mouth pressure?

Problem 15.61 Part A A drinking straw 20 cm long and 3.0 mm in diameter stands vertically in a cup of juice 8.0 cm in diameter. A section of straw 6.8 cm long extends above the juice. A child sucks on the straw, and the juice level begins dropping at 2.2 mm/s By how much does the pressure in the child's mouth differ from atmospheric pressure? Express your answer using two significant figures. AP Submit My Answers Give Up Part B What is the greatest height above the water surface from which the child could drink, assuming this same mouth pressure? Express your answer using two significant figures. cm max Submit My Answers Give Up

Answer 1

Length of the straw, L -0.2 nm Diameter of the straw 3x10-3m Diameter of the cup -8x10-m Speed, v 2.2x10m/s Part A Applying Bemoulli's principle, Using the relation,

TD 4 兀D Substituting, 4 2(8x10-2 )211 O-T) 丁1-1 |+103 9.8x 6.8x10-2 -0.5×1000×(2.2×10-3 -10,9 1890 Pa =1.9×10-3 Pa Part B Greatest height occurs when -Om/s R-R 1890 1000×9.8 =19cm