A ping-pong ball remains dancing at a height in a vertical stream of water.Explain how?

A small ball was released from rest from a point on a friction less track which ends in a loop in the form of a circle of radius 20 cm. What is the minimum verticle height of the point release so that the ball can remain in contact with the loop as it moves along it?

Water rises to a height h in a glass capillary tube when dipped vertically. Explain what happens when a similar tube of length less than h is dipped vertically in water.

A ball is dropped from a bridge at height of 176.4m over a river. After 2 seconds a ball is thrown straight downwards. What should be the initial velocity of the second ball so that both hit the water simultaneously.

A water fall discharges 60 litres of water per sec from a vertical height of 200 m . Assuming that all the energy due to fall is converted to heat and is retained by the falling water , find (i) the quantity of heat produced per sec and (ii) rise in temperature of water .

An Airforce plane is ascending vertically at the rate of 100 km/h. If the radius of the Earth is r km, then how fast is the area of the Earth visible from the plane increasing at 3 min after it started ascending ? Given that the visible area A at height h is given by A = 2pi r^(2) (h)/(r + h) .

How long do the seeds remain alive after they are dispersed? Explain with example.