Find Specific Gravity of 8.3 kg Block in Water

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Homework Help Overview

The problem involves determining the specific gravity of an 8.3 kg block submerged in water, with the spring scale indicating a reading of 46.9 N. The context includes concepts of buoyancy and density calculations.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss how to find the density of the block without knowing its volume and explore the relationship between weight in air and weight in water.

Discussion Status

Multiple approaches to calculating the specific gravity and density have been presented, with some participants questioning the accuracy of their calculations. There is an ongoing exploration of the relationships between weight, volume, and density, but no consensus has been reached on the correct method or answer.

Contextual Notes

Participants express frustration over repeated incorrect answers and seek clarification on the steps involved in the calculations. There is an emphasis on understanding the underlying principles rather than just obtaining a solution.

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Homework Statement



A 8.3 kg block of some unknown material is suspended from a spring scale and submerged in water. The spring scale reads 46.9 N. What is the specific gravity of the block?




Homework Equations



SG = density of object/density of reference material (water = 1000 kg/m^3)

density = mass/volume

The Attempt at a Solution



How do I find the density of the object if I do not know its volume?
 
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Find the weight of the block mg in air.
Weight in water is given. Find loss of weight. That is equal to weight of the displaced liquid. From that you can find the volume of the block.
 
so...

weight in air = 8.3 * 9.81 = 81.42 N

differnce = 81.42 - 46.9 = 35.523 N (weight of displaced liquid)

Density = m/v so

1000 = 35.523/v ...v = .035523 (volume of block)

density of block = m/v = 8.3/.035523 = 233.65

SG ( of block) = 233.65/1000 = .233

I did this and I get the wrong answer
 
35.523 N is the weight of the displaced water. Find the mass of the displaced water. And then find the density of the block.
 
ok...

mass of displaced water is 3.21 kg

1000 = 3.21/v...v= 0.00321

Density of block = 8.3/0.00321 = 2585.669

SG = 2585.669/1000 = 2.585

Still getting wrong answer
 
can someone just show me the step by step solution please...That way I can know exactly know what I am doing wrong instead of doing the wrong steps over and over...TIA
 
35.523n/9.8 =---?
 
SG = 81.42/(81.42 - 46.9) = 2.36

Thanks for your help though
 
Now for the density of block...

D = 8.3/.0035 = 2.37 * 10^3 kg/m^3
 

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