What role does specific heat play in keeping a watermelon cool for a long time after removing it from a fridge on a hot day? `(AS_7)`

Objects A and B that are initially separated from each other and well isolated from their surroundings are then brought into thermal contact. Initially T_(A) = 0^(@)C and T_(B) = 100^(@)C . The specific heat of A is less than the specific heat of B . After some time, the system comes to an equilibrium state. the final temperatures are:

(i) A poor emitter has a large reflectivity . Explain why. (ii) A copper tumbler feels much colder than a wooden block on a cold day. Explain why. (iii) The earth would become so cold that life is not possible on it in the absence of the atmosphere. Explain why? (iv) Why clear nights are cooler than cloudy nights? Why does a piece of red glass when heated and taken out glow with green light? (vi) Why does the earth not become as hot as the sun although it has been receiving heat from the sun for ages? (vii) Animals curl into a ball when they are very cool. Why? (viii) Heat is generated continuously in an electric heater but its temperature becomes constant after some time. Explain why? (ix) A piece of paper wrapped tightly on a wooden rod is observed to get charred quickly when held over a flame as compared to a similar piece of paper when wrapped on a brass rod. Explain why? (x) Liquid in a metallic pot boils quickly whose base is made black and rough than in a pot whose base is highly polished . Why?

A player throwsa a ball upwards with an initial speed of 29.4 ms^(-1) . (i) What is the direction of acceleration during the upwared motion of the ball? (ii) What are the velocity and acceleration of the ball at the highest point of its motion? (iii) Choose the x=0 and t=0 to be the location and time of the ball at its highest point, vertically downward direction to be the positive direction of X-axis, and give the signs of positive, velocity and acceleration of the ball during its upward, and downward motion. (iv) To what height does the ball rise and after how long does the ball return to the player's hand?( Take g =9.8 ms^(-2) , and neglect air resistance).

A player throws a ball upwards with an initial speed of 29.4 ms^(-1) (a) What is the direction of acceleration during the upward motion of the ball ? (b) What are the velocity and acceleration of the ball at the highest point of its motion ? (c) Choose the x = 0 m and t=0 s to be the location and time of the ball at its highest point vertically downward direction to be the positive direction of x-axis and give the signs of position, velocity and acceleration of the ball during its upward and downward motion. (d) To what height does the ball rise and after how long does the ball return to the player's hands ? (Take g = 9.8 ms^(-2) and neglect air resistance).

The figure given below shows the cooling curve of pure wax material after heating. It cools from A to B and solidifies along BD . If L and C are respective values of latent heat and the specific heat of the liquid wax, the ratio L / C is

A steel tape Im long is correctly calibrated for a temperature of 27.0 ^(@) C . The length of a steel rod measured by this tape is found to be 63.0 cm on a hot day when the temperature is 45.0^(@) C .What is the actual length of the steel rod on that day? What is the length of the same steel rod on a day when the temperature is 27.0^(@) C ? Coefficient of linear expansion of steel = 1.20 xx 10^(-5) K^(-1) .

(a) Estimate the speed with which electrons emitted from a heated emitter of an evacuated tube impinge on the collector maintained at a potential difference of 500 V with respect to the emitter. Ignore the small initial speeds of the electrons. The specific charge of the electron, i.e., its e/m is given to be 1.76 xx 10^(11) C kg^(-1) . (b) Use the same formula you employ in (a) to obtain electron speed for an collector potential of 10 MV. Do you see what is wrong ? In what way is the formula to be modified?