![Page 1: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/1.jpg)
Lecture 34
![Page 2: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/2.jpg)
![Page 3: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/3.jpg)
Today: • More on Buoyancy
• Fish in unstable equilibrium
• An in-lecture question most
physicist get wrong…
• Fluid flow
![Page 4: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/4.jpg)
Two identical bricks are held under water. Brick A is just beneath
the surface of the water, while brick B is at a greater depth.
The force needed to hold brick B in place is
A. larger
B. the same as
C. smaller
than the force required to hold brick A in place.
A
B
![Page 5: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/5.jpg)
![Page 6: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/6.jpg)
![Page 7: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/7.jpg)
![Page 8: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/8.jpg)
Two identical glasses are filled to the same level with water.
One of the two glasses has ice cubes floating in it.
Which weighs more?
A. the glass without ice cubes
B. the glass with ice cubes
C. both weigh the same
![Page 9: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/9.jpg)
A boat carrying a boulder is floating on a lake. The boulder
is thrown overboard and sinks.
The water level in the lake (with respect to the shore):
A. rises
B. drops
C. stays the same
D. not enough info
![Page 10: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/10.jpg)
![Page 11: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/11.jpg)
Buoyancy and Fish
Fish adjust their density fish so that fish=water and
FB=Wfish ("neutrally buoyant"). How?
Teleost Fish use a Swim Bladder:
- flexible, membrane-enclosed bag of gas
- fish secretes gas into bag, changing Vfish and fish.
![Page 12: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/12.jpg)
![Page 13: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/13.jpg)
What happens if an initially neutrally
buoyant fish goes a little deeper (i.e., h) ?
p(h) Vbladder Vfish fish
fish FB < W fish sinks!
If it goes a little higher, it rises.
Equilibrium is unstable, and fish must
constantly adjust gas in bladder!
![Page 14: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/14.jpg)
Cuttlefish use a Cuttlebone:
![Page 15: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/15.jpg)
Cuttlefish use a Cuttlebone:
- Rigid, porous bone filled with gas and liquid
Does not compress
- Fish secretes gas into bone, changing fish,
but Vfish stays constant, regardless of h and
p(h).
Can maintain neutral buoyancy when
ascending or descending without adjusting
gas in cuttlebone (stable).
![Page 16: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/16.jpg)
http://video.google.com/videoplay?docid=5053807934424522294
![Page 17: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/17.jpg)
![Page 18: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/18.jpg)
![Page 19: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/19.jpg)
![Page 20: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/20.jpg)
Blood flows through an artery that is partially blocked by
deposits along the artery wall.
Through which part of the artery is the volume flow rate R the
largest?
A. the narrow part
B. the wide parts
C. the part upstream of the blockage
D. the part downstream of the blockage
E. same volume flow rate everywhere
![Page 21: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/21.jpg)
Blood flows through an artery that is partially blocked by
deposits along the artery wall.
Through which part of the artery is the flow speed v largest?
A. the narrow part
B. the wide parts
C. the part upstream of the blockage
D. the part downstream of the blockage
E. same volume flow rate everywhere
![Page 22: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/22.jpg)
R1=v1A1 R2=v2A2
Volume flow rate R = vA=const!
Continuity and Gorges
R=R1=R2=constant
![Page 23: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/23.jpg)
Upper Enfield
Glen:
![Page 24: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/24.jpg)
R1=R2=R3
v~(2gy)1/2
R1=v1A1
R2=v2A2
R3=R1
y=0
+y
![Page 25: Lecture 34 - Cornell Universityliepe/webpage/docs/Phys...Lecture 34 Today: • More on Buoyancy • Fish in unstable equilibrium • An in-lecture question most physicist get wrong…](https://reader036.vdocuments.site/reader036/viewer/2022063009/5fc124f0023bb1666125a80b/html5/thumbnails/25.jpg)
Taughannock
Falls