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Author Topic: 1600 lb bear  (Read 7381 times)
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luv2cris
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on: December 10, 2008, 02:13:39 am »

A 1600 pound polar bear is floating in seawater, which has a density of 64 lbs/ft3.  1/2 cubic foot of bear is above water.  Find the volume of the bear. 

Now, what I did was take  mass = density X  volume  and I got v = 25 cubic feet.  My teacher says this is wrong because 1/2 cubic foot is above water.  I dont understand what difference that makes.  If I put an 8 cubic foot block into water or hold it above in the air, the volume doesnt change.  It's still going to be 8 cubic feet.  right?
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lookang
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Reply #1 on: December 16, 2008, 02:02:53 pm » posted from:Singapore,,Singapore

From the diagram

allow acceleration =0

sum F = 0
 
upthrust = weight

Rowwater*g*Volumedisplaced= mass*g

64*g*[V - 0.5 ] = 1600*g

V = 25.5 ft^3 = Volume of solid (bear)


My assessment of your question:
Now, what I did was take  mass = density X  volume  and I got v = 25 cubic feet.
So you are saying the Volume bear is 25 ?
your mistakes are:
1. assume density of bear as density of water
2. use of formula mass = density*volume without the correct context

 
If I put an 8 cubic foot block into water or hold it above in the air, the volume doesnt change.  It's still going to be 8 cubic feet.  right?
your mistake is
1. lack of a diagram to help you visual and understand the problem

suggestion:
look at the way i solve the problem, do you see why i use
[V - 0.5 ] = Volumedisplaced ?
« Last Edit: December 16, 2008, 02:12:50 pm by lookang » Logged
Zhah001
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Reply #2 on: February 18, 2015, 07:01:04 pm » posted from:,Punjab,Pakistan

  WE WERE FACING NORTH AND THE RAINBOW THAT WE WERE LOOKING AT BEFORE WAS EAST OF US, AT OUR ELEVATION AND HIGHER .  I,M NOT EXACTLY SURE BUT I BELIEVE THAT IT WAS MID TO LATE AFTERNOON.  I DO KNOW THAT WHEN EVER I LOOKED AROUND , IN EVERY DIRECTION , THERE WERE COLORS. AND ABOVE ME I COULD SEE LARGE WIDE BANDS OF COLORS. I HAVE NO EXPLANATION JUST A REAL MAGNIFICENT EXPERIENCE !  WISH I COULD MEET SOMEONE WHO'S HAD THIS HAPPEN TO THEM ?  OF COURSE ANY FEEDBACK IS WELCOMED.
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HyBriDe Dd
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