$200\, g$ of a solid ball at $20\,^oC$ is dropped in an equal amount of water at $80\,^oC$. The resulting temperature is $60\,^oC$. This means that specific heat of solid is
One fourth of water
One half of water
Twice of wate
Four times of water
$50\,g$ of copper is heated to increase is temperature by $10\,^oC$. If the same quantity of heat is given to $10\,g$ of water, the rise in its temperature is ........ $^oC$ (Specific heat of copper $= 420\,J-kg^{-1}\,^oC^{-1}$ )
$2\,g$ of steam condenses when passed through $40\,g$ of water initially at $25\,^oC$. The condensation of steam raises the temperature of water to $54.3\,^oC$, ........ $cal/g$ is the latent heat of steam ?
A lead bullet at $27\,^oC$ just melts when stopped by an obstacle. Assuming that $25\%$ of heat is absorbed by the obstacle, then the velocity of the bullet at the time of striking is ........ $m/s$ ( $M.P.$ of lead = $327\,^oC$, specific heat of lead $= 0.03\,cal/g\,^oC$, latent heat of fusion of lead $= 6\,cal/g$ and $J = 4.2\,joule/cal$ )
Liquid oxygen at $50\ K$ is heated to $300\ K$ at constant pressure of $1\ atm$. The rate of heating is constant. Which of the following graphs represents the variation of temperature with time ?
Explain why :
$(a)$ a body with large reflectivity is a poor emitter
$(b)$ a brass tumbler feels much colder than a wooden tray on a chilly day
$(c)$ an optical pyrometer (for measuring high temperatures) calibrated for an ideal black body radiation gives too low a value for the temperature of a red hot iron piece in the open, but gives a correct value for the temperature when the same piece is in the furnace
$(d)$ the earth without its atmosphere would be inhospitably cold
$(e)$ heating systems based on circulation of steam are more efficient in warming a building than those based on circulation of hot water