Level 5: Work and kinetic energy

Energy and power · level 5 of 8 · rough age 12-13 (a guide for parents; anyone can start anywhere)

In this level energy gets its formulas. You meet work, \(W = Fd\), the way a force passes energy on; kinetic energy, \(\tfrac12 mv^2\); and gravitational potential energy, \(mgh\). You use them to find how fast a dropped spanner hits the ground on Mars and on Earth, and how far a moving cart slides before friction stops it.

Lesson	You will be able to
Work, W = Fd	Calculate the work a force does, and say when a force does no work
Work at an angle	Use \(W = Fd\cos\theta\) for a force at an angle to the motion
Kinetic energy	Use \(E_k = \tfrac12 mv^2\), and see where it comes from
Gravitational potential energy	Use \(E_p = mgh\) on Mars and on Earth
A dropped tool	Use energy to find the speed of something falling, on Mars and on Earth
The work-energy theorem	Use net work = change in kinetic energy to find stopping distances

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