01
Work and the work–energy theorem
Why is ½mv² the combination that matters, and not mv or mv³?
Classical · Module 03
Classical Mechanics II — Energy, Momentum, Rotation
The shift from forces to conservation laws. Instead of integrating the whole messy interaction, you compare the before and the after — which is why this module feels like a cheat code.
By the end of this module
You can solve problems where the forces are unknown, using conserved quantities alone.
0%0 / 7 complete
02
Potential energy and conservation
What does it mean for energy to be 'conserved' if I cannot point at it?
ReadingFree
Feynman Lectures I-4: Conservation of Energy ↗Caltech
The 28-blocks parable. If you read one thing in this module, read this.
03
Momentum, impulse, and collisions
Why does momentum survive collisions that destroy kinetic energy?
InteractiveFree
Collision Lab ↗PhET
Set elasticity to 0 and watch momentum hold while energy does not.
04
Rotational kinematics and dynamics
Why does the same mass resist spinning differently depending on where it sits?
05
Angular momentum and gyroscopes
Why does a spinning top refuse to fall?
VideoFree
Gyroscopic Precession ↗Veritasium
The clearest physical explanation of why the torque turns the axis instead of tipping it.
06
Universal gravitation and Kepler's laws
Can one inverse-square law produce all three of Kepler's rules?
ReadingFree
Feynman's Lost Lecture — the elliptical orbit, geometrically ↗Caltech
Newton proved the ellipse with geometry alone. It is worth seeing once.
Check yourself
End-of-module quiz
Every answer comes with the reasoning, not just a verdict. Getting one wrong and reading why is the point.
01A 2 kg ball at 3 m/s strikes a stationary 4 kg ball and they stick together. The final speed is:
02Two objects of equal mass, a solid disc and a hoop, roll from rest down the same ramp. Which reaches the bottom first?
03A skater pulls her arms in and spins faster. Her kinetic energy:
Answer all 3 to finish the module.