This little climber climbs almost effortlessly balancing gravity and friction, using only straws as support.
- Poster board (at least 14 cm x 14 cm)
- String (1.5 m or more, depending on the height of the climb)
- Drinking straw
- 1 or 2 coins
- Pens/Coloring crayons
- 2 Paper clips
- Prepare the string by hanging it over a doorknob, a hook, or some other source of support that will allow the string to hang from a slightly elevated position.
- Draw your design of the climber on the cardboard and cut it out.
- Cut out the figure from cardboard.
- Decorate the figure as you wish. Be creative! Have fun!
- Cut 2 pieces, 2 cm long, from the straw.
- Tape the straws on the climber. When the climber is standing, the straws should be at an angle of 45 degrees from the floor, pointing the middle top of the climber and up to 10 cm apart (see picture at the top of the screen). Press hard to reinforce the straw.
- Tape a coin onto your climber. This adds some weight so the climber returns down when you let go.
- Thread the string through the straws.
- Tie one paper clip to each end of the string so that the climber doesn’t fall off when coming back down.
- Pull on the strings gently with both hands. Now pull one string down while gently releasing the other string. Switch sides. The climber will start to climb, first tilting one way then the other. Repeat pulling on each side of the string. Your climber should be climbing up the string!
- To bring your climber down, hold the two ends of the string without pulling. The climber should slide back down. Add another coin, if the climber doesn’t slide easily.
The science behind the scene:
This experiment showcases the balance between gravity and friction.
As one of the strings is pulled, the climber tilts and more friction is provided between the straw and string on one side, while allowing the string to slide through the straw on the other side to a more elevated position. By altering tugging on each side, the straw on the string is held fixed on one side while rising higher on the other. By repeating this step on both sides, the position of the climber rises on the string causing it to climb.
If the climber is light enough, the friction provided by the straw on the string prevents it from sliding back down, however if more weight is added to the climber, the effect of gravity is stronger. If the climber becomes too heavy, the friction between the straw and string is not enough to overcome the effects of gravity, and the climber slides back down.
Keep on experimenting:
- Does the angle of the straw make a difference to how fast the climber can climb, or whether the climber can climb at all?
- Does the weight of the climber affect how it climbs? (how fast, how easily, etc)
- What else can you think of that would affect how fast the climber climbs or slides (ie the material of the string or straw, etc).