Author Archives: hangtime
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Converting Between Angular & Linear Motion
This video covers what to do when linear quantities like velocity (m/s) are in the same problem as angular quantities (ω, radians, rad/sec, etc). This happens all the time in problems about cars and bikes, where they'll give you the distance driven or how fast the car is going and then ask you to figure out how fast the wheels are spinning. Also a cool problem: giving you the length (linear) of a string wrapped around a shaft (angular motion).
This topic covers what to do when linear quantities like velocity (m/s) are in the same problem as angular quantities (ω, radians, rad/sec, etc). This happens all the time in problems about cars and bikes, where they'll give you the distance driven or how fast the car is going and then ask you to figure out how fast the wheels are spinning. Also a cool problem: giving you the length (linear) of a string wrapped around a shaft (angular motion).
Gear Ratio Rotational Kinematics Problems
If you've ever ridden a bike, you've experienced a gear ratio (technically cogs): the larger front gear turns slower than the gear on the back wheel. This video has examples about bikes and wind mills (which also have gears in them), analyzing the angular velocity and acceleration of one gear compared to the other.
Basic Rotational Kinematics Problems (Angular Motion)
This video covers examples about how to use the rotational kinematics formulas to solve for angular acceleration, angular velocity, and angular displacement (Θ). If the formulas in the video don't look familiar, you should definitely watch the first video on this page first.
This chapter starts with a video full of examples about how to use the rotational kinematics formulas to solve for angular acceleration, angular velocity, and angular displacement (Θ). The second video is about gear ratios, calculating the angular acceleration and velocity of on gear when you are given information about the other gear (or bike sprocket) that it's driving.
Explainer: Angular vs Linear Motion Quantities
I've found that the best way to introduce rotational motion concepts to students is to first explain how similar they are to the kinematics you learned back at the beginning of physics. Same equations. Similar symbols. And best of all, rotational problems are always one-dimensional! No more of that X & Y component clutter to worry about.
Angular Quantities Are Vectors
This video explains something kind of non-intuitive: all these rotational quantities (ω, α, Τ) are vectors that point along the spin axis. Which direction along the spin axis? "Into the page" or "out of the page"? Just as the right hand rule!
Right Hand Rule In Rotational Motion & Torque
In physics there are like at least 5 different right hand rules that I can think of off the top of my head. This video relates only to the one where you use your right hand to figure out whether a given torque, angular velocity, or angular acceleration is positive or negative.
Vocab: Frequency in Angular Motion (Rotating Bodies)
Your professor might not do this, but there are a few out there who sometimes use the word "frequency" in place of "angular velocity" or "omega" (ω). In this video I just explain quickly what frequency means in this context, and I work a few conversion problems.
Units of Angular Velocity, Acceleration, & Displacement
In this video I explain the units of each of the variables (aka "quantities") you'll see in rotational motion and kinematics problems, and I work some examples of how to convert between the different units you'll see, especially for angular velocity (ω).
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.
Impulse vs Work: How to Know Which to Use?
Unfortunately for you, momentum and energy are always on the same exam. Why is that a bummer? Because the problems look almost EXACTLY the same. And yet if you try and solve an impulse problem with work and energy - or a work and energy problem with impulse - you will find yourself in a world of kinematic hurt. So this video focuses on only one thing: the easy way to spot which problem is which.