CONCEPT ROUND QUEST 2007-08 PHYSICS QUESTIONS1. The gravitational force of the Moon causes tides to occur, because of which the points A and B on the ocean, collinear with the line joining the centres of the Earth and the Moon, bulge out. But because of the rotation of the Earth the tidal bulges shift causing tidal oscillations, which eventually get dissipated as heat. What is the source of this heat loss? Whose energy is going down?2. In the winters, if you put a room heater on and watch its shadow on a wall, you will distinctly see the shadow of the hot air current rising. But looking directly at the heater or nearby regions, you do not see any wave like changing pattern. Why?3. In a uniform field B, if you let a pendulum made of copper sheet oscillate (fig. 2), it stops very soon. But a pendulum made of copper sheet with a comb like structure (fig. 2) oscillates for a longer duration. Why?4. Water flowing out of a hose-pipe held at an angle, say 750 is seen to exhibit the following behavior. If the flow rate is high, then the jet of water after
traveling some distance breaks up into several droplets. If the flow rate is low, this does not happen. Why?5. In principle, we can have an electric generator using a thermocouple, one end kept at the equator and the other end at the Antarctica. Does it mean that after a while the equator will become cooler at the expense of Antarctica becoming hotter? Or, is the source energy something else?6. We have all seen shiny black objects, e.g. well-polished shoes. These objects are shiny presumably because they reflect light in a certain manner. But ... black objects, by definition, are supposed to absorb all incident light. So how are the two properties consistent?