# This Physics Problem is killing me!!!

Discussion in 'MCAT: Medical College Admissions Test' started by roxy123, Mar 24, 2007.

1. ### roxy123 New Member

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So, this question is from Examkrackers, and i've been working on ti for like hours...and i still dont understand the explanation given in the back of the book....if anyone can help me out with a step by step, in formula calculations and how you plugged it in...i would forever thank you!!!

1) A 2 kg object submerged in the unknown fluid has an apparent loss of mass of 0.5 kg. What is the specific gravity of the object? (Specific gravity of fluid= 5)

Thank you so much ahead of time.....Please show me how to do it with numbers....so i can thoroughly understand it!! =) Cheers!

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3. ### Playmakur42 7+ Year Member

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1) A 2 kg object submerged in the unknown fluid has an apparent loss of mass of 0.5 kg. What is the specific gravity of the object? (Specific gravity of fluid= 5)

Step 1 - Find Density of Mystery Fluid
Sp. Grav. of fluid (5) = Density of fluid/Density of Water (1g/millilter)
Density of fluid= 5g/milliliter

Step 2 - use that information in the Buoyant Force Equation to solve
F of Buoyancy = Density of Fluid x Gravity X Volume of Fluid Displaced by Object

The F of Buoy that the system exerts is equal to the loss mass given in the question stem (.5kg) x the force of gravity (10) = 5N
We've already solved for density of the fluid
Gravity is (10)
Now we solve for Volume of Fluid Displaced.

5 = 5 x 10 x V disp
Vdisp=.1

Step 3 - Solve for Density of object since we know it's volume
D=M/V D=2kg/.1 D=20

Step 4 - Solve for specific gravity of object
Sp. Grav. Obj = Density of Object (20)/ Density of Water (1)

Sp. Grav. of Obj = 20

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5. ### Playmakur42 7+ Year Member

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The specific gravity of water is not 5 though, it's 1.

The submerged object loses .5 kg of mass in the mystery fluid, not in water, so I'm curious how you got the .5kg figure. If you divide the sp. grav. of water (1) by 10, you get .1 ..... not .5

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