Challenge someone: you have four cups and three knives. Three of the cups are in a triangle, too far apart for the knives to reach. You need to build a bridge to support the weight of the fourth cup.
What you need:
- 4x cups
- 3x knives
What to do:
- Place a knife from one cup pointing to the centre of the cups.
- Place a second knife from another cup into the centre of the cups, so the tip goes underneath the first knife.
- Place the third knife from the third cup into the centre of the cups, put it underneath the second knife, but put the tip above the first knife.
- Once the knives are secure, place the last cup on top.
What happens:
Each knife has to go over and under another knife. Positioning the knives like this causes an equal force on all three knives. The force is acting upwards and downwards. This allows objects (even heavier than an empty cup) to be balanced on the point where the knives intersect.
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