A solid sphere of density $\mathrm{\eta }$ ( > 1) times lighter than water is suspended in a water tank by a string tied to its base as shown in fig. If the mass of the sphere is m, then the tension in the string is given by:

      

1. $\left(\frac{\mathrm{\eta }-1}{\mathrm{\eta }}\right)\mathrm{mg}$                              

2. $\mathrm{\eta mg}$

3. $\frac{mg}{\mathrm{\eta }}$                                       

4. $(\mathrm{\eta }-1)\mathrm{mg}$

A boat carrying steel balls is floating on the surface of water in a tank. If the balls are thrown into the tank one by one, how will it affect the level of water?

A candle of diameter d is floating on a liquid in a cylindrical container of diameter D (D>>d) as shown in figure. If it is burning at the rate of 2cm/hour then the top of the candle will:
            

The velocity of kerosene oil in a horizontal pipe is 5 m/s. If $\mathrm{g}=10\mathrm{m}/{\mathrm{s}}^2$, then the velocity head of oil will be:
1. 1.25 m
2. 12.5 m
3. 0.125 m                             
4. 125 m

An L-shaped tube with a small orifice is held in a water stream as shown in fig. The upper end of the tube is 10.6 cm above the surface of water. What will be the height of the jet of water coming from the orifice? Velocity of water stream is 2.45 m/s.
         

1. Zero                                         
2. 20.0 cm                   
3. 10.6 cm                                   
4. 40.0 cm
 

An incompressible fluid flows steadily through a cylindrical pipe which has a radius 2r at point A and a radius r at B further along the flow direction. If the velocity at point A is v, its velocity at point B is:
1. 2v                               
2. v
3. v/2                               
4. 4v

 A wooden block with a coin placed on its top, floats in water as shown in fig. The distance l and h are shown there. After some time the coin falls into the water. Then:
                      

A wooden stick 2 m long is floating on the surface of the water. The surface tension of water is 0.07 N/m. By putting soap solution on one side of the stick, the surface tension is reduced to 0.06 N/m. The net force on the stick due to surface tension will be:

The energy needed to break a drop of radius R into n drops of radii r is given by:

1. $4\mathrm{\pi T}({\mathrm{nr}}^2-{\mathrm{R}}^2)$

2. $\frac{4}{3}\mathrm{\pi }({\mathrm{r}}^3\mathrm{n}-{\mathrm{R}}^2)$

3. $4\mathrm{\pi T}({\mathrm{R}}^2-{\mathrm{nr}}^2)$

4. $4\mathrm{\pi T}({\mathrm{r}}^2\mathrm{n}+{\mathrm{R}}^2)$

Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by $75\times {10}^{-4}$ $\mathrm{N}$ force due to the weight of the liquid. If the surface tension of water is $6\times {10}^{-2}$ ${\mathrm{Nm}}^{-1}$, the inner circumference of the capillary must be:

1. $1.25\times {10}^{-2}$ $\mathrm{m}$ 

2. $0.50\times {10}^{-2}$ $\mathrm{m}$

3. $6.5\times {10}^{-2}$ $\mathrm{m}$

4. $12.5\times {10}^{-2}$ $\mathrm{m}$