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 (Vavg=ΔX/Δt) or the more common instantaneous velocity equations from kinematics.
Average Velocity Problems
Vavg=ΔX/Δt or Vavg=(Vi+Vf)/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.
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.
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.
Average Acceleration Problems
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.
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.
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!
1-D Vertical (Gravity) Kinematics Problems
V=V0y+gt & Y=Y0+V0yt+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?"
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!"
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.
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)