Gravitation force is required for

Steam is passed into $22\, g$ of water at $20\,^oC$ . The mass of water that will be present when the water acquires a temperature of $90\,^oC$ is ............ $\mathrm{gm}$ (Latent heat of steam is $540\, cal/gm$)

A body cools from $60\,^oC$ to $50\,^oC$ in $10\, minutes$. If the room temperature is $25\,^oC$ and assuming Newton's law of cooling to hold good, the temperature of the body at the end of the next $10\, minutes$ will be ....... $^oC$

Two large holes are cut in a metal sheet. If this is heated, distances $AB$ and $BC$, (as shown)

Two rigid boxes containing different ideal gases are placed on a table. Box $A$ contains one mole of nitrogen at temperature $T_0$, while box $B$ contains one mole of helium at temperature $(7/3)$ $T_0$. The boxes are then put into thermal contact with each other, and heat flows between them until the gases reach a common final temperature (Ignore the heat capacity of boxes). Then, the final temperature of gases, $T_f$, in terms of $T_0$ is

The spectrum of a black body at two temperature  $27\,^oC$ and $327\,^oC$ is shown in the figure. Let  $A_1$ and $A_2$ be the areas under the two curves respectively. The value of $\frac {A_2}{A_1}$ is