Two capillary tubes of the same length but different radii $r_1 and r_2$ are fitted in parallel to the bottom of a vessel. The pressure head is p. What should be the radius of a single tube that can replace the two tubes so that the rate of flow is same as before

1. $r_1+r_2$

2. $\frac{r_1{r}_1}{r_1+r_2}$

3. $\frac{r_1+r_2}{2}$

4. None of these

A wooden block, with a coin placed on its top, floats in water as shown in fig. the distance $\ell$ and h are shown there. After some time the coin fails into the water, then

1. $\ell$ decreases and h increases

2. $\ell$ increases and h decreases

3. Both $\ell$ and h increase

4. Both $\ell$ and h decrease

A solid ball of density half of that of water falls freely under gravity from a height of 19.6 m and then enters into water. Upto what depth will the ball go ?

1. 9.8 m

2. 19.6 m

3. 39.2 m

4. 29.4 m

Water rises in a capillary tube to a certain height such that the upward force due to surface tension is balanced by 75 x 10^-4 N force due to the weight of the liquid. If the surface tension of water is 6 x 10^-2 N/m, the inner circumference of the capillary must be

1. 1.25 x 10^-2 m

2. 0.50 x 10^-2 m

3. 6.5 x 10^-2 m

4. 12.5 x 10^-2 m

A cubical block of wood 10 cm on a side floats at the interface between oil and water as shown in figure with its lower face 2 cm below the interface. The density of oil is 0.6 gm/cm³. The mass of the block is

1. 600 gm

2. 680 gm

3. 800 gm

4. 200 gm

Angle of contact of a liquid with a solid depends on

1. solid only

2. liquid only

3. both on solid and liquid only

4. orientation of the solid surface in liquid

A U-tube is partially filled with water. Oil which does not mix with water is next poured into one side, until water rises by 25 cm on the other side. If the density of oil is 0.8, the oil level will stand higher than the water level by

1. 6.25 cm

2. 12.50 cm

3. 31.75 cm

4. 62.50 cm

Two solid spheres of same metal but of mass M and 8M fall simultaneously on a viscous liquid and their terminal velocities are v and nv, then value of n is 

1. 16

2. 8

3. 4

4. 2

A liquid will not wet the surface of a solid, if the angle of contact is

1. 0$°$

2. 45$°$

3. 60$°$

4. >90$°$

Drops of a liquid are usually more spherical in shape than larger drops of same liquid because

1. force of surface tension is equal and opposite to force of gravity

2. force of surface tension predominates the force of gravity

3. force of gravity predominates the force of surface tension

4. force of gravity and surface tension are equal and in same direction