Work (in Physics)

What The Heck Is Work?

This video tries to explain what "work" means in physics in simple, regular words. Mostly work is a measure of how much "effort" a person or machine has to put into making something happen, like pushing a box somewhere. There are a few non-intuitive situations where the amount of work is actually zero or negative, though, and of course those funky situations are the ones that tend to show up in multiple choice questions on exams.

Units of Work (Nm vs N^•m)

Joules are the metric units of energy, and work is energy, so Joules are also the unit of work. Does that make sense? This video is pretty short, but it gets into a bit more depth, including something that always puzzled me: why is it that to calculate both torque and work you multiply Newtons times meters, yet work is measured in Joules while torque is still Nm?

Calculating Work Done By A Force (& Kinetic Energy)

This video is kind of a grab-bag of a few different types of very common work problems, mostly involving something getting pushed or pulled across the ground. In this video I also try to help you get the hang of some of the wording of these problems, making sense of who's doing what work on or to whom. Also covered is a kinetic energy problem calculating work a foot does on a soccer ball based on the ball's final velocity.

Work Done Lifting Something

This video has a bunch of problems you can see diagrams for in the video thumbnail to the right. From pulley systems to crates getting dragged by winches to a person doing work against gravity by walking up a hill.

Work Done By Vectors

This video covers a very specific type of work problem where they give you force and displacement as vectors, then you take the dot product (scalar product) of the vectors to calculate the work. Most students get a little bit freaked when they see a problem with i's and j's in them, but in this case they're actually doing you a favor compared to the crazy wording of your typical work word problem.

Work Done By Variable Force

Most of the time you're doing a problem about work, it's a steady force that you're working against: friction, gravity, a winch pulling with steady force, etc. But sometimes a force changes as you go. So this video just explains the two methods for dealing with this: either add up the area under the curve using geometry, or find area by integration if they give you a formula for force as a function of x.

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