191.

Air of density 1.3 kg/m³ flows horizontally with a speed 106 km/h. A house has a plane roof of area 40 m². Find the magnitude of aerodynamic lift on the roof.

• 4.22 × 10⁵ N

• 2.25 × 10⁴ N

• 4.22 × 10³ N

• 2.25 × 10⁶ N

A boat strikes an under water rock which punctures a hole 5 cm in diameter in its hull which is 1.5 m below the water line. At what rate in litre per second does water enter.

• 2.65 Ls^-1

• 8.85 Ls^-1

• 10.65 Ls^-1

• 624 Ls^-1

Two soap bubbles A & B are kept in a closed chamber where the air is maintained at pressure 8 N/m² . The radii of bubbles A & B are 2cm and 4cm, respectively. Surface tension of the soap water used to make bubbles is 0.04 N/m. If n_A and n_B are the number of moles of air in bubbles A and B, respectively, then $\frac{{\mathrm{n}}_{\mathrm{B}}}{{\mathrm{n}}_{\mathrm{A}}}$ = ?[Neglect the effect of gravity]

• 2

• 8

• 9

• 6

By sucking through a straw, a student can reduce the pressure in his lungs to 750 mm of Hg (density 13.6 g/cm³). Using the straw, he can drink water from a glass upto a maximum depth of

• 10 cm

• 13.6 cm

• 75 cm

• 1.36 cm

A wooden block is floating on water kept in a beaker, 40% of the block is above the water surface. Now the beaker is kept inside a lift that starts going upward with acceleration equal to $\frac{\mathrm{g}}{2}$. The block will then

• sink

• float with 10% above the water surface

• float with 40% above the water surface

• float with 70% above the water surface

The neck and bottom of a bottle are3 cm and 15 cm in radius respectively. If the cork is pressed with a force 12 N in the neck of the bottle, then force exerted on the bottom of the bottle is

• 30 N

• 150 N

• 300 N

• 600 N

A wooden block, with a coin placed on its top, floats in water as shown in the figure. The distances h and l are shown there. After sometime, the coin falls into the water. Then

• both l and h increase

• both l and h decrease

• l decreases and h increases

• l increases and h decreases

A square wire frame of size L is dipped in a liquid. On taking out a membrane is formed. If the surface tension of liquid is T, then force acting on a frame will be

• 2T L

• 4T L

• 8T L

• 16T L

A 20 cm long capillary tube is dipped in water. The water rises up to 8 cm. If entire arrangement is put in a freely falling elevator, the length of water column in the capillary tube will be

• 4 cm

• 8 cm

• 10 cm

• 20 cm

A metal plate of area 10³ cm² rests on a layer of oil 6 mm thick. A tangential force of 10^-2 N is applied on it to move it with a constant velocity of 6 cms^-1. The coefficient of viscosity of the liquid is

• 0.1 poise

• 0.5 poise

• 0.7 poise

• 0.9 poise