Classroom Activity for 11-14
What the Activity is for
This activity is for introducing free-body force diagrams and to help students develop their vocabulary for describing forces.
What to Prepare
Download a set of colour-safe cardboard arrows (below) and print and cut out enough so that each pair of students has a set. You will also need to choose some objects in everyday situations to draw force diagrams for. Search online or prepare props to illustrate each. Three examples are shown below:
- Write the following description framework on the board: “The ___________ arrow represents the _______________ force that acts on the ____________ due to the _____________”
- Show a photo or demonstrate one situation (you could start with a drinks can sitting on a table).
- For each situation ask students to:
- Identify the object and draw it by itself
- Use same-sized arrows if two forces are the same size
- Point each arrow in the direction of the force
- Stick the base of each arrow to the place where the force acts (it's okay for their arrows to overlap)
- Use the description framework to discuss what each arrow represents with their partner
As students build force diagrams, circulate and use questioning to encourage them to explain and progress their thinking (eg: What force does that arrow represent? What causes it? Where does it act?)
For the three examples above, the force diagrams may look like:
This activity can also be a useful introduction to Newton’s third law. Ask students to draw diagrams of the other object involved in the interaction (e.g. Earth) and use the same colour of arrow for matching force pairs (e.g. green arrows for the gravitational force on both Earth and the football). Using the description framework will help students see that if there is a force on object A due to B, there is an equal and opposite force on B due to A.
Colour-safe force arrows