Net work energy concept

1. Dec 10, 2008

caljuice

I've been confused about work. I know it equals F x D. But what is F? Is it the netforce or the force being exerted.

If you are pushing up an object up an incline with 200N and the opposing force of gravity + friction is 100N for D=20m. Is Work, Fnet x D or 200N x D?

Does the same apply to the Worknet in this equation --> delta = $Worknet=$ke + $pe + Wf If I wanted to find$ke and had wf and pe and the components of work. Would I use Fnet or force thats moving the object.

I always thought it was Fnet but some questions have been confusing me. Thanks

2. Dec 11, 2008

tiny-tim

Hi caljuice!

You only need to know the work done so that you can use the work-energy theorem …

so you have to include all the forces (that do work) … gravity, friction, pushing forces, everything.

(The normal force, of course, does no work)

If the body isn't rotating (so all its parts have the same velocity), then you can either multiply the net force by distance, to get "net work", or you can calcualte the work done by each force separately.