What The Heck Is Impulse?
This video quickly explains what the heck impulse is, how it is related to momentum, and how all that is similar to work & energy.
Author Archives: hangtime
The videos in this chapter cover all the typical impulse problems you see: golf balls, baseballs, cars, etc. Mostly, though, I spend a lot of time explaining what you REALLY need to know about impulse: how the heck to tell when to use impulse (and momentum) vs when to use work (and energy)!
Rocket Thrust Momentum Problems
Rockets aren't covered by every intro physics class, but to me they are the coolest thing about momentum. I don't know about you, but I love watching SpaceX launches (and landings), it's just freaking unbelievable, and the more you know about the physics underlying those things, the crazier it is that the whole thing is even possible!
Momentum In Explosions (items breaking apart)
Most momentum problems involve two items colliding. This video covers the other type, where two items start together but separate at high speed, so it's kind of like an inelastic collision in reverse. The examples covered include calculating the recoil of a cannon as it fires a bullet, and a figure skater giving his partner a push so she can launch a triple axle.
2-D Elastic Collisions (momentum & energy)
Two-dimensional elastic collisions are no picnic, so if you see one of these on a test, I pity you. On the other hand, if the only problem you have trouble with on your energy & momentum exam is this one, you're probably setting the curve in your class anyways, so don't cry too big a river.
2-D Inelastic Collision Problems (momentum only)
Two-dimensional inelastic collisions are a lot like 2-D force problems: everything has to be broken up into X and Y components. On the bright side, it's inelastic, so at least nothing is squared like it is for elastic collisions. The example in this video is the classic "two cars collide at 90° then stick together" problem.
1-D Elastic Collisions (momentum and energy)
This video covers the famous billiard ball problem which every professor and book uses as an example for elastic collisions in one dimension. Elastic collisions are not your friend, because even though momentum is conserved (easy), you have to also use the conservation of energy (harder, since everything is squared).
1-D Inelastic Collisions (momentum only)
The most basic conservation of momentum problems are the inelastic ones where the two objects "stick" together or become "entangled" after they collide. After I show you the algebraic trick for these, you'll mock these if you see one on a test.
Conservation of Momentum (Collisions) In A Nutshell
Like conservation of energy problems, every momentum problem is kind of the same: plug the numbers from the problem into the conservation of energy equation and hope you can solve for the thing they're asking for. There are a few tricks, though, so this video gives you "the view from 10,000 feet" of momentum problems, before digging into the nitty gritty in the rest of the momentum videos.
This chapter covers all the different types of momentum and collision problems you're likely to see: 1-dimensional, 2-dimensional, elastic, inelastic, billiard balls, figure skaters, cannons, etc.
Exact Answers vs Approximate Answers
This video covers a quick topic that usually first comes up when you're learning factoring or the quadratic formula, but will keep popping up as you learn rational exponents and any other situation where roots and radicals are involved.
This video covers a quick topic that usually first comes up when you're learning factoring or the quadratic formula, but will keep popping up as you learn rational exponents and any other situation where roots and radicals are involved.
Sketching Parent Graphs from Derivative Graphs
Normally, they're going to ask you to sketch derivative graphs based on the parent. I've gotten emailed from time to time about the opposite direction, though, so here goes. WARNING: When you move in the "up" direction, going from derivatives to the parent function, you are either told a point to start from (initial condition) or you're just guessing. But the principles are useful, so here they are.
Partial Derivatives
This video explains the basics of partial derivatives, how to find them, their notation, and how to tell if a function is continuous based on its partial derivatives.
The video in this chapter explains the basics of partial derivatives, how to find them, their notation, and how to tell if a function is continuous based on its partial derivatives.
Euler's Method vs Slope Fields
This video is a clip from the larger Euler's Method video which explains the difference between slope fields and Euler. Just thought I'd break it out into a separate video since if you're wondering about slope fields, you probably don't need to watch Euler's video.
Euler's Method
This video covers Euler's Method, from A to Z. First we get into what it is and why the heck we're doing this: it's on the test. Well, actually there's another reason: often differential equations can't be solved with calculus or any other method, so all you can do is "approximate" the answer using the methods we're learning here. I work the problems two ways - with tables and without - with different step sizes.
Slope fields and Euler's Method are actually pretty similar, so the videos in this chapter explain how to manage both.
Work-Energy Theorem Roller Coaster Problem
This problem should maybe have been in the roller coaster video above, but I'm giving it its own video because it is conceptually a bit different from the other roller coaster problems. Most roller coaster problems don't have friction or work, but this one does (brakes slowing down the roller coaster). I also discuss what would have happened if instead the work had accelerated the cars.
Work-Energy Theorem (W=ΔKE+ΔPE)
The Work Energy Theorem is all about conservation of energy. Really it's just another way to write the equation I prefer, which is Ein=Eout. But some teachers really believe in always starting with this thing, so this video covers that and reminds you to be careful of the sign you put on work.