Work & Friction

For our classmates who are out travelling today I thought I'd take a quick few taps of the keyboard to answer a question regarding the work done when friction is present.

As the last few chapters have trained us to do, we look at situations from the perspective of a free body diagram (didn't know this did you). When we have a free body diagram we usually look at it from the perspective of the NET FORCE acting on it (or vice versa-if you're thinking NET FORCE on an object you're thinking of a free body diagram).

When it comes to our topic of WORK a free body diagram is not necessary (hence neither is the net force). Work is defined as the product of Applied force on an object, and the object's displacement (later there'll be a cosine of the angle between the force and the displacement, but for now we'll consider force and displacement to be in the same direction).



So, back to the question at hand, "How does friction effect the work done on an object?"

Your answer is, "It doesn't affect it at all." Even if the net force on an object is zero, it may still be moving with a constant velocity (thanks Mr. Newton). If it's moving with a constant velocity, the object will have a displacement. As the object has a displacement, and a force was applied through that displacement, then the person who applied that force has done work.

Hope that was helpful. Have a great weekend.