8. The outside dimensions of a rectangular box(top open) made of aluminium are 24x12x4 inches. the wall thickness of the bottom and the sides is x. derive an expression that relates the weight of the box and the wall thickness x. determine the thickness x for the box that weighs 15 lbs. The specific weight of the alumininum is 0.101 lb/cubic inch.

Question:The outside dimensions of a rectangular box(top open) made of aluminium are 24x12x4 inches. the wall thickness of the bottom and the sides is x. derive an expression that relates the weight of the box and the wall thickness x. determine the thickness x for the box that weighs 15 lbs. The specific weight of the alumininum is 0.101 lb/cubic inch.  

Using Matlab 7.0 software

%in script file

w=15;

gama=0.101;

Val=w/gama;

a=[-2 24];

b=[-1 4];

c=[-1 4];

Vin=conv(c,conv(a,b));

polyequation=[0 0 0 (Val-24*12*4)]+Vin

r=roots(polyequation);

%in command window

>> wallthickness

polyequation =

   -2.0000   40.0000 -224.0000 -619.4851 




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