A lead bullet at $27\ ^oC$ just melts when stooped by an obstacle. Assuming that $25\%$ of heat is absorbed by the obstacle, then the velocity of the bullet at the time of striking ....... $m/s$ ( $M.P.$ of lead $= 327\,^oC$ , specific heat of lead $= 0.03\,cal/g\,^oC$ , latent heat of fusion of lead $= 6\,cal/g$ and $J = 4.2\,joule/cal$ )
A lead bullet at $27\ ^oC$ just melts when stooped by an obstacle. Assuming that $25\%$ of heat is absorbed by the obstacle, then the velocity of the bullet at the time of striking ....... $m/s$ ( $M.P.$ of lead $= 327\,^oC$ , specific heat of lead $= 0.03\,cal/g\,^oC$ , latent heat of fusion of lead $= 6\,cal/g$ and $J = 4.2\,joule/cal$ )
- A
$410$
- B
$1230$
- C
$307.5$
- D
None of the above
Similar Questions
Six identical conducting rods are joined as shown. The ends $A$ and $D$ are maintained at $200\,^oC$ and $20\,^oC$ respectively. No heat is lost to surroundings. The temperature of the junction $C$ will be ........ $^oC$
Six identical conducting rods are joined as shown. The ends $A$ and $D$ are maintained at $200\,^oC$ and $20\,^oC$ respectively. No heat is lost to surroundings. The temperature of the junction $C$ will be ........ $^oC$
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
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
Three perfect gases at absolute temperature $T_1 , T_2$ and $T_3$ are mixed. The masses of molecules are $m_1 , m_2$ and $m_3$ and the number of molecules are $n_1 , n_2$ and $n_3$ respectively. Assuming no loss of energy, the final temperature of the mixture is
Three perfect gases at absolute temperature $T_1 , T_2$ and $T_3$ are mixed. The masses of molecules are $m_1 , m_2$ and $m_3$ and the number of molecules are $n_1 , n_2$ and $n_3$ respectively. Assuming no loss of energy, the final temperature of the mixture is
The temperature of a body on Kelvin scale is found to be $x\,K.$ When it is measured by Fahrenheit thermometer, it is found to be $x\,^oF$ , then the value of $x$ is
The temperature of a body on Kelvin scale is found to be $x\,K.$ When it is measured by Fahrenheit thermometer, it is found to be $x\,^oF$ , then the value of $x$ is
A coffee maker makes coffee by passing steam through a mixture of coffee powder, milk and water. If the steam is mixed at the rate of $50 \,g$ per minute in a mug containing $500 \,g$ of mixture, then it takes about $t_0$ seconds to make coffee at $70^{\circ} C$ when the initial temperature of the mixture is $25^{\circ} C$. The value of $t_0$ is close to .......... $s$ (ratio of latent heat of evaporation to specific heat of water is $540^{\circ} C$ and specific heat of the mixture can be taken to be the same as that of water)
A coffee maker makes coffee by passing steam through a mixture of coffee powder, milk and water. If the steam is mixed at the rate of $50 \,g$ per minute in a mug containing $500 \,g$ of mixture, then it takes about $t_0$ seconds to make coffee at $70^{\circ} C$ when the initial temperature of the mixture is $25^{\circ} C$. The value of $t_0$ is close to .......... $s$ (ratio of latent heat of evaporation to specific heat of water is $540^{\circ} C$ and specific heat of the mixture can be taken to be the same as that of water)
- [KVPY 2018]