Fd vs, Fdcos0

[DieselD]

When do you use W=Fd vs. W=Fdcos(theta)?

Hope you guys understand my question.

---

Members don't see this ad.

 

[RoadRunner17]

Fdcos is used when the force being applied isn't in the same direction as the direction the work is being done in.

Remember: cos of 0 is 1. so when the force is being applied fully in the same direction as the work is being done, then it reduces to W = Fd.

 

[misterex]

You should always use Fdcos(theta). It's just that sometimes F and d are in the same direction so cos (0)=1 and W=Fd.

 

[xlr8]

The theta is there because the only part of the force that matters is the component that is helping you go in the direction that you are going in.

A good (but tricky) example of this is work done by a magnetic field. Force of a magnetic field is: F (vector) = q<v x B>.

Cross product only involves the perpendicular components. This means that the force from a magnetic field on a charged particle will always be perpendicular. Since the force is perpendicular to the direction its going, theres no work, theta = 90.