Rishi Desai, M.D. has released the first videos in a new series looking at how the pressure created by your heartbeat moves blood through your heart.

Pressure in the Left Heart - Part 1

Pressure in the Left Heart - Part 2

Pressure in the Left Heart - Part 3

Karl Wendt looks into how DC motors work and shows you how you can build your own. He also demonstrates the motor controller he used in building Bit-zee bot.

Brushed DC motor explained

Build your own motor

Compare the hair dryer motor to the one you can build.

And here are videos about the motor controller for Bit-zee bot:

Build a motor controller for your Bit-zee bot

Why does Bit-zee need a motor controller?

Sal has created new algebra videos to explain solving systems of equations:

Trolls, Tolls, and Systems of Equations

Then check out the follow-up videos on Solving the Troll Riddle Visually and Solving Systems Graphically.

Elimination

The King’s planning a party and needs your help figuring out how many cupcakes to order.

King’s Cupcakes: Solving Systems by Elimination

This video leads into the first exercise on elimination, which has a new guide video: Simple Elimination Practice.

Then, the King needs more party planning help in managing The Potato Chip Issue:

How many bags of potato chips do people eat?

This leads into the next exercise on elimination, which also has a new companion video.

Substitution

Next, a little bird visits the King to teach him a new solving method: substitution.

Talking bird solves systems with substitution

The exercise using substitution has a new companion video.

Solutions to Systems

Sal then investigates special situations you may run into, including systems without a solution:

Inconsistent systems of equations

and systems with infinite solutions:

Infinite solutions to systems

Our exercise on how many solutions a system of equations has also comes with a new companion video.

Instructor Brit Cruise has created two new videos and computer science programs as part of his Prime Adventures series, where he explores deeper properties of prime numbers through building algorithms that perform prime factorization and primality tests.

Level 4: Sieve of Eratosthenes

Try out the CS program that goes with “Level 4.”

Level 5: Primality test using the Sieve of Eratosthenes

Try out the CS program that goes with “Level 5.”