Question

1) If you toss a stone in still water, concentric circled are formed. what form will waves have if a stone is tossed into smoothly flowing water?

2) Which has the greater amount of internal energy- an iceberg or a cup of hot coffee? defend your answer.

3) When a 1kg metal pan containing 1kg of cold water is removed from the refrigerator and set on a table, which absorbs more heat from the room?

I forgot the last question:

4) what is the ultimate source of energy in coal, oil, and wood? why do we call energy from wood renewable but energy from coal and oil nonrenewable?

Answer 1

1) Smoothly flowing water will move forward with a constant velocity. Smoothly flowing every particle flow is independent of other particle for like a laminar flow type.

So, when a stone is dropped in smoothly flowing water, concentric circles will be formed and due to the translation of water particles concentric circle will also move ahead with the same velocity of flowing water. This is because except for translation of particle there are no force or disturbance.

2) A cup of hot coffee will have the greater amount of internal energy.

Internal energy is defined as total heat contained in the system. A cup of coffee and iceberg both contains mostly water but coffee is at higher temperature than an iceberg, so cup of coffee should have more energy.

For a clear understand, let us consider that the both given material are made from water when it was at a state colder than the temperature of water. Consider this as the base to which we compare the facts.

Two sample of this base material (ice) is, one is converted into iceberg and other is used to make a coffee. Change in internal energy strongly depends on the temperature difference. It is clear that temperature difference is greater for coffee, so coffee will have greater change in internal energy and its final internal energy will be greater than iceberg.

3) Cold water has higher specific heat (in KJ/(Kg-K) than metal pan. So, the cold water will require more heat to reach the thermal equilibrium with the room temperature. Therefore, heat absorb by water will be higher than metal pan.