Figure 10 shows a test-tube inverted and floating inside a plastie bottle containing some water. The bottle is then sealed.

Question

Figure 10 shows a test-tube inverted and floating inside a plastic bottle containing some water. The bottle is then sealed.

It is observed that when the sides of the bottle are squeezed, the test-rube sinks. 
Explain this observation

Answer 1

Upon squeezing the sides of the bottle, the pressure inside the bottle increases forcing more water to enter the test-tube. this increases the average density of the test tube and its contents hence it sinks./ up-thrust decrease