1
Things that roll
Joyful Mathematics: Chapter 2
GoalTell which things roll when we push them.
New words
roll · turn over and over as it movespush · move something away from youslope · a path that goes down, like a ramp
Explanation
A round thing can roll. Push a ball and it rolls. A wheel rolls. An orange rolls too. A thing with flat sides and corners does not roll well. A ball put at the top of a slope rolls down by itself.
Worked examples
An auto rickshaw moves on round wheels. The wheels roll.
Put a ball at the top of a slope. Let go. It rolls down by itself.
A thing that rolls is round at least on one side. A brick has flat sides, so it does not roll.
Class activity
Roll race. Make a slope with a board or a thick book. Roll different things down: a ball, a tin, a pencil, a book. Which ones roll? Which stay still? Sort them into two groups.
Practice
1
Which one rolls: the orange or the brick?
The orange.
2
Which one has wheels that roll: the bicycle or the house?
The bicycle.
3
Does a brick roll well?
No. It has flat sides and corners.
4
Name two things at home that roll.
Any right answers, for example a ball and a tin on its side.