A wind with speed 40 m/s blows parallel to the roof of a house. The area of the roof is 250 m2. Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the force will be (Pair=1.2kg/m3)
1. 4.8x105N,downwards
2. 4.8x105N,upwards
3. 24x105N,upwards
4. 24x105N,downwards
Water rises to a height h in capillary tube . If the length of capillary tube is above the surface of water is made less than h, then
1. water rises upto the tip of capillary tube and then starts overflowing like a fountain
2. water rises upto the top of capillary tube and stays there without overflowing
3. water rises upto a point a little below the top and stays there
4. water does not rise at all
A piece of solid weighs 120 g in air, 80 g in water and 60 g in a liquid. The relative density of the solid and that of the liquid are respectively :
1. 3, 2
2. 2,
3. , 2
4. 3,
An inverted bell lying at the bottom of a lake 47.6 m deep has 50 cm3 of air trapped in it. The bell is brought to the surface of the lake. The volume of the trapped air will be: (atmospheric pressure = 70 cm of Hg and density of Hg = 13.6 g/cm3)
1. 350 cm3
2. 300 cm3
3. 250 cm3
4. 22 cm3
A siphon in use is demonstrated in the following figure. The density of the liquid flowing in the siphon is 1.5 gm/cc. The pressure difference between the point P and S will be:
1. | 105 N / m | 2. | 2 × 105 N / m |
3. | Zero | 4. | Infinity |
The height of a mercury barometer is 75 cm at sea level and 50 cm at the top of a hill. The ratio of density of mercury to that of air is . The height of the hill is:
1. | 250 m | 2. | 2.5 km |
3. | 1.25 km | 4. | 750 m |
A body of density d1 is counterpoised by Mg of weights of density d2 in air of density d. Then the true mass of the body is
1. M
2.
3.
4.
The value of g at a place decreases by 2%. Then, the barometric height of mercury:
1. | increases by 2%. | 2. | decreases by 2%. |
3. | remains unchanged. | 4. | sometimes increases and sometimes decreases. |
A barometer kept in a stationary elevator reads 76 cm. If the elevator starts accelerating up, the reading will be:
1. zero.
2. equal to 76 cm.
3. more than 76 cm.
4. less than 76 cm.
A closed rectangular tank is completely filled with water and is accelerated horizontally with an acceleration a towards right. Pressure is (i) maximum at, and (ii) minimum at
1. (i) B (ii) D
2. (i) C (ii) D
3. (i) B (ii) C
4. (i) B (ii) A