Calculating Work: When to Use W = Fd cos(a) vs. the Integral of F

[caspeerrr]

Homework Statement

When do you use W = Fd cos(a) and when do you use the integral of F?

Homework Equations

W = Fd cos(a) Integral of F

The Attempt at a Solution

When doing exercises it seems random to me when I have to use the formule W = fd cos(a) and when I have to use the integral? What is the consistency in this?
Thanks!

 

[berkeman]

Homework Statement

When do you use W = Fd cos(a) and when do you use the integral of F?

Homework Equations

W = Fd cos(a) Integral of F

The Attempt at a Solution

When doing exercises it seems random to me when I have to use the formule W = fd cos(a) and when I have to use the integral? What is the consistency in this?
Thanks!

It would help if you could give a few examples. Can you post 1-2 of each type of problem? In general you integrate if something is changing along the path of integration. If things are constant along the path (like pushing a block at a constant speed across a floor), then you can just use W=Fd.