It is observed that the temperature of the surroundings starts falling when the ice in a frozen lake starts melting. Give a reason for the observation.

What happens when a zinc rod is dipped in copper sulfate solution ? Give the reason for this observation.

When the rivers and lakes start freezing, the weather becomes warm. Give reason.

If the depth of a lake is 10 m, and the temperature of surroundings is -10^@C and that of water at the bottom of the lake is 5^@C . The thermal conductivity of the Ice and water are K_f and K_w respectively. The depth of ice will be

A body at temperature 40^(@)C is kept in a surrounding of constant temperature 20^(@)C . It is observed that its temperature falls to 35^(@)C in 10 minutes. Find how much more time will it taken for the body to attain a temperature of 30^(@)C .

A listener is at rest with respect to the source of sound. A wind starts blowing along the line joining the source and the observer. Which of the following quantities do not change?

Ice at 0^@C is added to 200 g of water initially at 70^@C in a vacuum flask. When 50 g of ice has been added and has all melted the temperature of the flask and contents is 40^@C . When a further 80 g of ice has been added and has all melted the temperature of the whole becomes 10^@C . Find the latent heat of fusion of ice.

The value of absolute temperature at which ice starts melting is

One end of the rod of length l, thermal conductivity K and area of cross-section A is maintained at a constant temperature of 100^@C . At the other end large quantity of ice is kept at 0^@C . Due to temperature difference, heat flows from left end to right end of the rod. Due to this heat ice will start melting. Neglecting the radiation losses find the expression of rate of melting of ice. .

The temperature of water in calorimeter is theta and the temperature of surrounding is theta_(0 ) ( lt theta) . Observation are recorded for temperature difference (theta- theta_0) and time t. The cooling curve is best represented in graph.

A stationary man observes that the rain is falling vertically downwards. When he starts running a velocity of 12 kmh^(-1) , he observes that the rain is falling at an angle 60^(@) with the vertical. The actual velocity of rain is