Question:

Answer:

0:24 shows that the mass of the plasticine boat is 100 g.

0:40 shows that the plasticine boat displaces 100 cm^-3 water. This is expected because to support the weight of 100 g, 100 g of water must be displaced. (Remember that density of water is 1 g cm^-3)

0:53 shows that the crushed plasticine boat displaces only 50 cm^-3 water. As a plasticine ball with a volume of 50 cm^-3, it can at most displace 50 g of water. Even when it is fully submerged, the upthrust exerted by the water is still not enough to support its weight. This explains why it sank.

Btw, the density of plasticine can be worked out to be 100 g divided by 50 cm^-3 = 2 g cm^-3, which is about twice the density of water.

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