Level 3: Balanced and unbalanced

Forces and motion · level 3 of 8 · rough age 9-10 (a guide for parents; anyone can start anywhere)

In this level you learn to draw forces as arrows and to add them up. When the forces on something balance, it keeps doing what it was doing; when they don't, it speeds up, slows down or turns. You meet the newton, the unit of force, and the spring that measures it, and find out why a bathroom scale would tell a lie on Mars.

Lesson	You will be able to
Force arrows	Draw a force as an arrow with the right direction and length, and label it
Balanced forces	Spot balanced forces and say what they do to something still or moving
Unbalanced forces	Find the overall force when forces don't balance, and say what it does
The newton	Use the newton as the unit of force, and find the weight of a kilogram on Mars and Earth
Springs that measure force	Explain how a spring measures a force, and read a newton meter
Weighing on Mars	Explain why a balance gives the same answer on Mars but a spring scale does not

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