Lesson 7 of 7

Forces and motion

Goal: Describe how forces change speed and direction.

Puzzles for this lesson

A resultant force changes how an object moves. Balanced forces leave its motion as it is.

Resultant force forwards: the object speeds up. Backwards: it slows down. Sideways: it changes direction.
Balanced forces on a still object: it stays still.
Balanced forces on a moving object: it keeps going at a steady speed in a straight line. A stone on smooth ice slides a long way because there is so little friction to slow it.

Your turn

This lesson’s activity starts here in a moment.

I can predict the motion of an object when the forces on it change.I can say what an unbalanced force does.

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Force A push or a pull

Friction Opposes sliding between two surfaces

Resultant force The single force left when forces are combined

Balanced forces Equal and opposite forces on one object

For teachers: AQA 3.1.1, 3.1.3 · Pearson Edexcel 41.1 · Cambridge 8Pf.03