Find the length of a roll of GI steel sheet given its weight

  • #1
escape_velocity
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Homework Statement


I have a roll of galvanized iron sheet steel.
Its width is 19mm and thickness 0.25mm
Density 7850 kg/m^3
Weight of the roll is 75kg
I want to find how long would be the roll if its unwound.

Homework Equations


Density D = M / V
Length L = V / A
Area A = Width * Thickness

The Attempt at a Solution



I need to find the volume of the material first,
so I find the cross sectional area A from the length and thickness
A = 0.000005 m^2

For finding volume I know that D = 7850 kg / m^3 but I need to find mass (M)
So here is where I'm stuck up
Should I use Mass as 75kg
or Do I need to calculate Mass from the Weight which is 75 kg.
using W = m * g or m = W/g
even in this equation so m would be 75 / 9.8 = 7.65kg.
The final answer I have is Length = 200m but I don't know if that is correct.
 

Answers and Replies

  • #2
Baluncore
Science Advisor
2021 Award
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Do a quick check.

What does one metre weigh in kg? ( 1 * 0.019 * 0.00025 * 7850 ) = 0.0372875 kg
So the length is ( 75 / 0.0372875 ) = 2011.39 m

Where is the missing factor of 10 ?

What is the difference between a force a weight and a mass?
Consider units; newton, kg force and kg mass.
 
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