Core
Translational Kinetic Energy
Definition: \(K=\tfrac12 mv^2\) for a particle of mass \(m\) with speed \(v\).
- Speed vs velocity
- Units and scaling
- Doubling speed effect
Work & Energy · Physics
Kinetic Energy
Kinetic energy is the energy of motion: \(K=\tfrac12 mv^2\). It depends on your frame of reference.
This topic includes
Subtopics to master
Build the formula, then extend it to 2D motion and particle systems.
Frame
Dependence on Reference Frame
Because \(v\) depends on the observer, \(K\) can change when you change frames.
- Relative velocity
- Same event, different K
- What stays invariant (not K)
Geometry
Kinetic Energy in 1D and 2D
Use \(v^2=v_x^2+v_y^2\) to compute kinetic energy in 2D motion.
- Vector speed relation
- Projectile KE changes
- Component reasoning
Many particles
Kinetic Energy of Systems of Particles
Total kinetic energy is the sum over particles; later you’ll connect this to center-of-mass ideas.
- Sum of \(\tfrac12 mv^2\)
- Internal vs overall motion (preview)
- System bookkeeping
Practice
Practice & Exercises
Compute kinetic energy and interpret changes across frames and components.
- Compute K from v
- Compare K in different frames
- 2D component drills
- Multi-particle total K sets
- Short reasoning questions
Bridge
Preparing for Work–Energy
Once you know \(K\), you can connect forces to motion changes using net work: \(\Delta K\).
- Energy change viewpoint
- Net work idea
- Next topic setup