Coin game

Free-play sliding coins into each other, or play a game of tabletop billiards with coins, to demonstrate motion, friction, energy transfer and action-reaction. Shorten into a fast demonstration.
Science content
Physics: Motion and Forces, Newton’s Laws, Gravity (K, 2, 6)
  • tabletop
  • optional: other surfaces to use or lay over tabletop e.g. carpet
  • about 20 coins, optionally foreign coins that the students will also like to inspect

This activity can be run as free play and/or a more organized game.

Free play:
Students are given the coins and asked to flick one across the table to hit another. They can experiment with changing the size of the coin that they flick and the coin that is hit, making a line of coins and flicking the end one, flicking the bottom coin of a stack, and other activities that they will invent.

Try flicking the coins across different surfaces (carpet, smooth floor, sand paper) and compare which slows down the coin most and which slows it down least i.e. which has most friction and which has least friction.

Coin game:
Two students sit opposite each other and make a goal with their index and little finger of one hand over the edge of the table. Each student starts with the same number of coins. Score goals by flicking coins into the opponent’s goal.
In every play a coin must hit another, and for a goal to count.
Coin is out of play when it it flicked off the table.
Final score when all the coins are in goals or off the table.
While the students play, ask them to notice how energy is transferred from one coin to another. At the end of the games, bring up the same concepts as in the free play Debrief above.

Games that involve similar transfer of energy: curling, billiards, boules.

Discussion of the forces and energy transfer:
The force of the finger hitting the coin makes it move.
The force of one coin hitting another makes the second coin move. As one coin hits another, energy is transferred from the first coin to the second coin, so that the first coin can move and the second coin stops moving. Depending on the relative sizes of the coins the second coin will move far or less far. If the flicked coin is small enough and the second coin large enough, the flicked coin may bounce off.

Coins stop moving along the table, even if they do not hit another coin, as some energy is lost as heat from friction between the coin and the tabletop, and some is dissipated as sounds waves.

For older students the coins act according to Newton’s Laws of Motion:
First Law: Any object will stay still, or continue to move in a straight line, unless an external force acts on it (e.g. finger hitting coin, coin hitting another coin).
Second Law: Larger force or a larger object will alter the speed of motion of an object (flicking harder, or using different-sized coins will alter how far the coin moves).
Third Law: An object will have an equal and opposite reaction to the force applied to it (the coin pushes back on the finger when it moves forward).


Try altering the slope of the table, so that one player is flicking up-hill - does this affect the movement of the coins? If so, can add the force of gravity to the discussions.

Grades taught
Gr K
Gr 1
Gr 2
Gr 3
Gr 5