Round to tens: 240 + 370 = 610
round to hundreds: 200 + 400 = 600
hope this helps
Second moment of area about an axis along any diameter in the plane of the cross section (i.e. x-x, y-y) is each equal to (1/4)pi r^4.
The second moment of area about the zz-axis (along the axis of the cylinder) is the sum of the two, namely (1/2)pi r^4.
The derivation is by integration of the following:
int int y^2 dA
over the area of the cross section, and can be found in any book on mechanics of materials.
I = / r where I = current and r = resistance
80 = k / 50 so
k = 400
so we have I = 400/r
when r = 40
I = 400/40 = 10 amps
First third and last answer