Can rice hold a bamboo stick?
Warning! Only under adult supervision
- plastic bottle;
Fill a plastic bottle to the brim with rice. Then, closing the opening with one hand, tap the bottle on the table several times to make the rice settle in place. The volume of rice in the bottle should decrease. Add more rice and tamp it down again. Then insert a chopstick into the rice and try to pull it back out again. The stick lifts the bottle easily!
Frictional force arises when two bodies come into contact and interferes with their movement relative to each other. In this experiment, the chopstick and the rice are two such bodies. When the rice is tamped down, it becomes quite dense, and when the chopstick is inserted the rice has nowhere to go: the bottle limits its movement. The rice squeezes the stick firmly from all sides and a strong frictional force arises, which is capable of supporting the bottle. It is worth noting that frictional force also arises if the rice is uncompressed, but it is much weaker, because the uncompressed rice presses less on the stick.
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