HKPHO questions (urgent!!!!!!)

1. Upthrust (or buoyance) depends on the density of fluid. The amount (depth) of fluid is not crucial.

6. The rotational motion would affect the linear velocity but not the acceleration of the centre of mass.

12. The image formed by the second lens (lens-2) acts as a virtual object to the inserted lens, thus producing a real image.

19. Option D has the largest contact surface, thus enabling charges to flow more easily.

2. This is Boyle's Law.
Before the can is inserted, the pressure is atmospheric Po, and Vo is the volume of the can, which is equa to the volume of air inside.

After the can is inserted, the air inside the can is compressed by the water pressure, thus reduced to volume V. The pressure of air inside the can must equal to the water pressure outside, which is (Po+pgh)

By Boyle's law, pressure x volume = constant
i.e. (Po).(Vo) = (Po+pgh).V

3. The value of 5.12 cm is found by averaging the five given data. You would find a more acurate result if the number of data points are more. Thus 5.12 cm is only an estimate of the actual distance. The true distance can only be determined if there are infinite (or very large number) of measurements.