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27 Nov 2019

Why does a needle need to be dry to float on water? I'm creatinga lesson plan aimed at a 5th grade class, so the answer doesn'tneed to be too difficult or in-depth.

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Collen Von
Collen VonLv2
27 Nov 2019

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

A cylindrical container of lenghtL is full to the brim with a liquid which has mass densityp. It is placed on a weigh-scale; the scale reading isW. A light ball which would float on the liquid if allowedto do so, of volume V and mass m is pushed gentlydown and held beneath the surface of the liquid with a rigid rod ofnegligible volume.

(a) What is the mass ofthe liquid which overflowed whilethe ball was being pused into the liquid?

(b) What is the reading of the scale when the ball isfully immersed after the water that overflowed has been removedfrom the scale?

(c) If instead of being pushed down by rod, theball is held in place by a thin tring attached to the bottom of thecontainer. What is the tension T in the string, and whatis the reading on the scale after the water that overflowed hasbeen removed from the scale?

I think that for part a the answer would be m=pV because

V=volume of ball = volume of water displaced

and p=m/v

I'm stuck on parts b and c. For part b I started solving it andit seems that the ball wouldn't exert any force on the scale.

Another solution that I came up with is that the force boyancywoud need an equal and opposite reaction force- from newtons laws.Then the scale would read: W-pV+force boyancy?

For part c I'm really stuck. It's in an equilibrium so: forceboyancy= tension+ weight?

Weight on scale = W- pV +???

Thanks!

I think it's a simple problem, but don't have the book to look upthe equations I need right now. I particularly want to understandpart b. Any help is appreciated.

Swimmers can feel the pressure inrease on their ears as they swimto the bottom of the pool.

a. Calculate the pressure in atmospheres (absolute) at the bottomof the pool (depth = 3m) on a day when the barometric pressure is0.95 atm.

b. If the swimming pool were filled with salt water instead offresh water, would the pressure at 3 m be the same, higher, orlower? Why?

Question: "A diving bell is a 3-m tall cylinder closed at the upperend but open at the lower end. The temperature of the air in thebell is 20 degrees C. The bell is lowered into the ocean until itslower end is 100m deep. The temperature at that depth is 10 degreesC.

a. How high does the water rise in the bell after enough time haspassed for the air inside to reach thermal equilibrium?

I solved this by doing pV=nRT for the air in the bell both for whenit's on land and for when it's in the ocean. Then I found the ratioof the Vs in each situation and used this to get that the waterrises 2.73m up into the bell.

b. A compressed-air hose from the surface is used to expel all thewater from the bell. What minimum air pressure is required to dothis?

I'm stuck and really confused. Won't the air add moles of gas aswell as pressure? Also, whenever the system in thermal equilibrium,Pin = Pout. So won't Pin just be 10.9 atm, the pressure at thatdepth of water?

The Cramster textbook solution basically says "P2 = P1 +(waterdensity)(g)(waterheight). Looks like something about equalforces, but I don't get it.

THANKS!!

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