Author Archives: hangtime

Spring Conservation of Energy Problems

Since you'll almost never ONLY be asked to calculate the potential energy of a spring for a given displacement, so the problems in this video incorporate spring potential energy into energy problems involving pendulums and projectiles (if a kid on a pogo stick can be considered a projectile).

This video appears on the page: Conservation of Energy

Roller Coaster Conservation of Energy Problems

Based on the teachers around here, roller coasters are a very popular type of test question because you can add so much to it, like centripetal force. The most classic question in this video is to calculate the initial height of a roller coaster so that the cars will make it through a loop-to-loop of radius R.

This video appears on the page: Conservation of Energy

Pendulum & Tarzan Conservation of Energy Problems

In this video we do pendulum problems using conservation of energy, NOT the later physics techniques involving simple harmonic motion (ω, period, etc). Stuff like calculating the speed of a pendulum at the bottom of its arc, or figuring out how high or how fast can swing given an initial height or velocity.

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Ramp Conservation of Energy Problems

In this video we use conservation of energy to much more easily solve some ramp problems that were a lot more work in the Forces chapters: objects sliding down a ramp with and without friction, a truck smashing up a runaway truck ramp, and a snow boarder getting air in a halfpipe. If problems are easier with energy than with forces and kinematics, why did your teacher wait until now to introduce energy? To make you suffer.

This video appears on the page: Conservation of Energy

Potential Energy (mgh & springs)

This video covers potential energy in general, so you've got your gravitational potential energy and spring potential energy, plus a bunch of other examples that you can put down if your next exam requires a list! (It probably won't.)

This video appears on the page: Conservation of Energy

Kinetic Energy

Think you already know everything there is to know about kinetic energy? Then this video probably isn't for you. This is more of an intro, with a quick problem calculating the speed a baseball would need in order to have the same kinetic energy as a bus (classic question).

This video appears on the page: Conservation of Energy

Conservative vs Nonconservative Forces

In addition to explaining the definition and a few examples of conservative forces and non-conservative forces, in this video I also go through the example of swimming across a swirling pond to give you a more hands-on example of how this actually works.

This video appears on the page: Conservation of Energy

Conservation of Energy In A Nutshell

This video gives you the big picture on how to solve conservation of energy problems. I don't work any actual examples in this one because I want to introduce the concept for you and explain how all these problems are pretty much the same. I also dabble in the Work-Energy Theorem, which some professors make a big deal about and others pretty much ignore.

This video appears on the page: Conservation of Energy

Conservation of Energy &
The Work Energy Theorem:
roller coasters, ramps, pendulums, Tarzan problems, springs, cars, kinetic energy, potential energy, conservative forces, non-conservative forces, Work-Energy Theorem
W=ΔKE+ΔPE

This chapter has ten videos covering every nook and cranny of Conservation of Energy. Personal favorites are Tarzan problems (pendulum problems in disguise) where the legendary jungle master swings up, down and sideways. Roller coasters are a teacher fave, because the roller coaster is going the same speed at all the places on the track that are at a given height, so you can do cool stuff like throw an unexpected centripetal force or work-energy theorem problem on the end. And of course we cover the basics like kinetic energy, spring potential energy, gravitational potential energy, conservative vs non-conservative forces, and runaway truck ramps.

Part of the course(s): Physics

Power & Energy Unit Conversions

If you're already a master of dimensional analysis & unit conversions, then you can probably don't need this video. But since some older/British units of energy and power can be kind of crazy looking, if you have a book or professor who doesn't stick to SI units, this video should give you some confidence in wading through the mess of conversion factors in the back cover of your textbook.

This video appears on the page: Power in Physics

Power Calculation Examples (& Efficiency)

If you only watch one power video, I'd actually recommend the intro video above this one. But if you're in a rush and jamming through homework, I guess you might as well stop here. Besides calculating power in a bunch of situations, it also addresses the topic of efficiency, which is a common part b of power problems. If you make it to the last problem, which is a doozy, you also learn a bit about max power and the relationship between power and velocity.

This video appears on the page: Power in Physics

Light Bulb Power (and Why Edison Bulbs Suck)

This video isn't necessary for your physics class, but if you're a big fan of Edison-style light bulbs (pictured to the right), you might want to see this considering how those bulbs are taking over our houses, coffee shops and restaurants! (Hint: not good from a physics and efficiency standpoint.)

This video appears on the page: Power in Physics

Intro to Power (Power vs Force vs Work)

This video gives you an overview of power that you'll definitely want before you tackle these problems. Besides explaining common misconceptions and preparing you for multiple choice questions about power, it also explains how to approach word problems about power, work, and kinetic energy.

This video appears on the page: Power in Physics

Power:
power vs work vs force, efficiency, unit conversions, Edison bulbs P=W/t, P=F•v

In many physics classes, power is one or two problems. In others, they make it more complicated. These videos cover Power in enough depth that you can handle the tough stuff, but it also makes it easy for you to skim and get what you need. And for those of you aspiring to be architects, designers, or restaurant entrepreneurs, as a bonus you also get a video about why Edison bulbs are your worst nightmare from a power and efficiency standpoint.

Part of the course(s): Physics

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.

This video appears on the page: Work

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.

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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.

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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.

This video appears on the page: Work

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?

This video appears on the page: Work

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.

This video appears on the page: Work