Terminal Velocity

Q.

A rain drop falls near the surface of the Earth with almost uniform velocity because

1. Its weight is negligible

2. The force of surface tension balances its weight

3. The force of viscosity of air balances its weight

4. The drops are charged and atmospheric electric field balances its weight

Q. A small spherical body of radius $r$ is falling under gravity in a viscous medium and due to friction, the medium gets heated. When the body attains terminal velocity, then the rate of heating $\frac{dH}{dt}$ is proportional to $r^n$. Find the value of $n$.

Q. In an industrial process 10 kg of water per hour is to be heated from ${20}^{\circ }Cto{80}^{\circ }C.$ To do this steam at ${150}^{\circ }C$ is
passed from a boiler into a copper coil immersed in water. The steam condenses in the coil and is returned to
the boiler as water at ${90}^{\circ }C.$ how many kg of steam is required per hour.
(Specific heat of steam = 1 calorie per gm°C, Latent heat of vaporization = 540 cal/gm)

1. 1 gm
2. 10 gm
3. 10 kg
4. 1 kg

Q. Two liquids A and B are at ${32}^{\circ }C$ and ${24}^{\circ }C.$ When mixed in equal masses the temperature of the mixture is
found to be ${28}^{\circ }C.$ Their specific heats are in the ratio of

1. 2 : 3
2. 3 : 2
3. 1 : 1
4. 4 : 3

Q. 2 kg of ice at $-{20}^{\circ }C$ is mixed with 5 kg of water at ${20}^{\circ }C$ in an insulating vessel having a negligible heat capacity. Calculate the final mass of water remaining in the container. It is given that the specific heats of water and ice are 1 kcal/kg per ${}^{\circ }Cand0.5kcal/kg{/}^{\circ }C$ while the latent heat of fusion of ice is 80 kcal/kg

1. 4 kg
2. 2 kg
3. 6 kg
4. 7 kg

Q. Work done in converting one gram of ice at $–{10}^{\circ }C$ into steam at ${100}^{\circ }C$ is

1. 6056 J
2. 721 J
3. 3045 J
4. 616 J

Q. When 300 J of heat is added to 25 gm of sample of a material its temperature rises from ${25}^{\circ }Cto{45}^{\circ }C.$ the thermal capacity of the sample and specific heat of the material are respectively given by

1. 
2. 
3. 
4. 

Q.

Heat required to convert one gram of ice at $0^{\circ }C$ into steam at ${100}^{\circ }C$ is (given $L_{stream}$ = 536 cal/gm)

1. 100 calorie

2. 0.01 kilo calorie

3. 716 calorie

4. 1 kilo calorie

Q. A beaker contains 200 gm of water. The heat capacity of the beaker is equal to that of 20 gm of water. The
initial temperature of water in the beaker is ${20}^{\circ }C.$ If 440 gm of hot water at ${92}^{\circ }C$ is poured in it, the final
temperature (neglecting radiation loss) will be nearest to

1. 
2. 
3. 
4. 

Q.

80 gm of water at ${30}^{\circ }C$ are poured on a large block of ice at $0^{\circ }C$. The mass of ice that melts is

1. 30 gm

2. 80 gm

3. 1600 gm

4. 150 gm