$A$ drilling machine of $10 \, kW$ power is used to drill a bore in a small aluminium block of mass $8 \, kg$. If $50 \%$ of power is used up in heating the machine itself or lost to the surroundings,then the rise in temperature of the block in $2.5 \, minutes$ is ........ $^\circ C$. [Specific heat of aluminium $= 0.91 \, J/g \cdot ^\circ C$]

How much thermal energy is required to change a $40 \ g$ ice cube from solid at $-10^{\circ} C$ to steam at $110^{\circ} C$ (in $kcal$)?
[Assume, latent heat of fusion for water $= 80 \ kcal/kg$, specific heat of water $= 1 \ kcal/kg^{\circ} C$, specific heat of ice $= 0.5 \ kcal/kg^{\circ} C$, specific heat of steam $= 0.48 \ kcal/kg^{\circ} C$, latent heat of vaporisation of water $= 540 \ kcal/kg$]

$A$ hailstone at $0^{\circ}C$ falls from a height of $1\, km$ on an insulating surface,converting the whole of its kinetic energy into heat. What part of it will melt? (Take $g = 10\, m/s^2$,$J = 4.2\, J/cal$,and latent heat of fusion of ice $L = 80\, cal/g = 80 \times 10^3\, cal/kg$)

$A$ lead bullet at $27\ ^oC$ just melts when stopped by an obstacle. Assuming that $25\%$ of heat is absorbed by the obstacle,the velocity of the bullet at the time of striking is ....... $m/s$. (Melting point of lead $= 327\ ^oC$,specific heat of lead $= 0.03\ cal/g\ ^oC$,latent heat of fusion of lead $= 6\ cal/g$,and $J = 4.2\ J/cal$)

$A$ closed bottle containing water at $30^{\circ} C$ is opened on the surface of the moon. Then,

$A$ waterfall is $84 \ m$ high. If half of the potential energy of the falling water gets converted to heat,the rise in temperature of the water will be: (in $^\circ C$)