Physics Practice 5/8

Kinetic energy (capstone)

From /guides/energy-forces-and-motion: kinetic energy is the energy of motion, KE = 0.5 * m * v^2. The guide calls out that speed counts double - going twice as fast carries four times the kinetic energy - and the squared v in this formula is exactly why: doubling v doubles v^2 twice over. It's the same reason high speeds are so much more dangerous than they feel.

The starter expression uses small numbers - swap in this lesson's real ones.

Your task: a 70 kg cyclist is moving at 8 m/s. Using KE = 0.5 * m * v^2, what's their kinetic energy, in joules?

You'll practice:

Substituting real values into KE = 0.5 * m * v^2
Seeing the squared term's effect: try doubling v in your head and notice the answer more than doubles

0.5 * 10 * 2^2