# Working with Force and Mass

Hello All,

This problem comes from the book: Fundamentals of Engineering Thermodynamic.

I actually have the answer attached, but I am looking for some help understanding it.

From a non-calculus perspective, I can put the equation into this form with the position (z) left as a variable.

F = [ 7800 - 360*(z/2) ] * [$$\pi$$*(0.25^2)] * [9.78]

But I am having real trouble understanding how to solve for z.

## The Attempt at a Solution

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From a non-calculus perspective, I can put the equation into this form with the position (z) left as a variable.

F = [ 7800 - 360*(z/2) ] * [$$\pi$$*(0.25^2)] * [9.78]

But I am having real trouble understanding how to solve for z.
What do you mean 'from a non-calculus perspective'? You need calculus to solve for the mass of the cylinder. You're not solving for z, z is the position along the cylinder.

Hint: Think of the cylinder as composed of disks of thickness dz. What's the mass of each disk? Integrate to get the total mass of the cylinder.