Pushes, Pulls and Magnets
Why a rolling ball always stops, whether a magnet can pull through a table, and how far a paper clip will jump. Three lessons on the pushes and pulls that start, stop and steer things.
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3 lessons in this unit
Lesson 1 · 45–60 minWhy does a ball stop rolling?Teams roll the same ball down the same ramp onto a hard floor, a carpet and a towel, and measure how far it goes each time. They find out that a rolling ball doesn't just run out of go: something rubs against it and slows it down.
Lesson 2 · 45–60 minCan a magnet work through a table?Teams test whether a magnet can pull a paper clip through paper, foil, plastic, cloth and wood, then count how many cards it can pull through before it lets go. They find out that most materials don't block a magnet at all: distance is what weakens the pull.
Lesson 3 · 45–60 minHow far will a paper clip jump?Teams slide a magnet slowly toward a paper clip along a ruler and measure the gap at the moment the clip jumps. They repeat it, use the pattern to predict what two and three magnets will do, and then design a magnet gadget that works without touching.
Students roll balls down the same ramp onto different floors and find out what really stops them. Then they test whether a magnet’s pull can pass through paper, foil, plastic and a tabletop, and measure the distance at which a paper clip leaps to a magnet. Every lesson uses balls, books, paper clips and ordinary classroom magnets.
By the end of the unit, students can explain that things don’t start, stop or change direction without a push or a pull, that friction is a force that slows things down, and that a magnet can pull on some objects without touching them, more strongly when they are close. They finish by designing a simple magnet gadget for a real problem.