Author Archives: hangtime

Terminal Velocity

This video is basically a non-stop ad for the 90's classic movie Point Break, but in so promoting it also gives you some insight into Terminal Velocity (a lesser 90's movie that's also about skydiving). Also mentioned briefly: what terminal velocity is, how to graph it, and what you need to know about it for your next test.

Horizontal 1-D Kinematics Problems

V=V₀+at    &    X=X₀+V₀t+½at²

This video covers one-dimensional motion problems that are in the horizontal direction (as opposed to objects being dropped), like buses and cars either speeding up or slowing down. And the final problem is a trick-laden doozie: "A bus leaves a stop. You hesitate three seconds before chasing it. Calculate how long it takes you to catch up!"

1-D Vertical (Gravity) Kinematics Problems

V=V_0y+gt    &    Y=Y₀+V_0yt+½gt²

This video covers one-dimensional problems where an object is either dropped or thrown vertically, i.e. straight up or straight down. No angles. No horizontal components. Just answering questions like "how long does a rock take to hit the ground when dropped off a 40-m tall building?" "What if it's thrown downwards at 20 m/s?" "What if it's thrown up at 30m/s?"

Overview of Equations of Motion (Kinematics)

This short video explains the kinematics equations and briefly summarizes how to spot the types of problems each is best for. A good video to add to your pre-test cram playlist!

Formula-Free Acceleration & Velocity Problems

For most physics students I work with (i.e. the normal, non-A+ people), physics isn't the problem: it's the formulas that confuse them and induce panic. So if you're not loving physics, I encourage you to watch this video, where we'll solve a few problems with common sense rather than getting lost in plug-and-chug land. Then in the next videos when we do the harder problems with formulas, hopefully the background in this video will give you a little bit more understanding and a little less panic.

Average Acceleration Problems

a_avg=ΔV/Δt

This video explains how to calculate acceleration (also known as average acceleration) from problems where they say how much something sped up or slowed down over a given period of time.

Constant Acceleration Explained

This short video explains why every problem in your typical physics class assumes constant acceleration, whether it says so or not. The even shorter version: Because otherwise you'd need calculus and integrals to solve every problem.

Units of Acceleration Explained

m/s²? How the heck can you square seconds? And calling them "meters per second per second" is even worse! This formula-free video explains all that. To help you get your head around these funky units, I start with a few basic problems using non-metric units that actually make a bit of sense to normal people.

Average Velocity Problems

V_avg=ΔX/Δt     or    V_avg=(V_i+V_f)/2

First, this video shows you how to use the first equation above to solve basic average velocity problems. Then I show you how to use the second equation to solve a particular type of trick question where they don't use the word "average" in the problem but most profs expect you to be able to solve. I also let you in on how to use the average velocity formulas above to solve almost any kinematics problem, which not everyone likes but some of my students really latch onto.

Instantaneous vs Average Velocity

In this video, first I explain the difference between these two types of problem. Then we'll go through a bunch of questions and just look at the wording to figure out if you're supposed to solve them using the average velocity equation (V_avg=ΔX/Δt) or the more common instantaneous velocity equations from kinematics.

Intro to One-Dimensional Kinematics (free)

Not sure what one-dimensional kinematics (motion) problems are? How are they different from two-dimensional problems? Which formulas are involved? This video helps you get oriented, introducing the videos from the 1-D kinematics chapter.

Relative Velocity Problems

This video covers the three types of relative velocity problem that every physics professor uses: conveyors, planes, and rowboats crossing rivers perpendicular to the current.

Relative Velocity Concepts

This video lays out the concept of relative motion in a way that will help you with short answer questions. It will also give you a lot of perspective on, like, The World, man.

Inertial Frames

Sometimes called "the inertial frame" if you want to sound cool, this video explains what it is, and a few concepts that are likely to show up on a short answer test question.

Coordinate Systems and Reference Frames

You may THINK you know coordinate systems (from algebra) and that they don't have much to do with physics. But you're going to want to watch this video and put them in all your sketches because: physics problems are REALLY hard, and teachers curve tests a lot. So how do coordinate systems help you? Partial credit, baby!

Angle of Elevation Problems

These are word problems which are designed to be confusing but are in fact just SohCahToa problems in disguise. They always involve someone looking at a distant object, noting the angle that they have to look up or down to see it, then using that angle to estimate either its height or its distance.

How To Combine Two Or More Vectors Using Components

These are some long, juicy problems. They give you two or three vectors, such as forces, each of which you must break into its X & Y components so that you can then sum up the X's and the Y's before recombining everything into the final resultant vector which is your answer. It's a mouthful.