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Homework Statement
The stress of a particular material, σ, is a function of x and y, where x is stress in the x-direction and y is stress in the y direction. the stress function is given by:
σ(x,y)= [itex]e^{y}[/itex] ln(2x+3y)
when x=2cm @ 3cm/s
y=3cm @ 1cm/s
Homework Equations
[itex]\frac{dσ}{dt}[/itex]=[itex]\frac{∂σ}{∂u}\frac{dx}{dt}+\frac{∂σ}{∂y}\frac{dy}{dt}[/itex]
∴[itex]\frac{dx}{dt}[/itex] = 3cm/s
and [itex]\frac{dy}{dt}[/itex] = 1cm/s
The Attempt at a Solution
Homework Statement
I have:
[itex]\frac{∂σ}{∂y}[/itex] = [itex]\frac{3}{2x+3y}[/itex]
and
[itex]\frac{∂σ}{∂x}[/itex] = [itex]\frac{2}{2x+3y}[/itex]
Homework Equations
Im not sure if these partial differentiations are correct.
The Attempt at a Solution
Homework Statement
carrying on asif they were:
[itex]\frac{dσ}{dt}[/itex]= [itex]\frac{3}{2x+3y}[/itex] (3) + [itex]\frac{2}{2x+3y}[/itex] (2)
sub rates in for x and y:
[itex]\frac{dσ}{dt}[/itex]= [itex]\frac{9}{2(3)+3(1)}[/itex] + [itex]\frac{4}{2(3)+3(1)}[/itex] (2)
Homework Equations
so summing up i end up with:
[itex]\frac{dσ}{dt}[/itex]= 1.44
I was wondering what the units would be? considering that the original problem states stress, I can't figure out what the units are?
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