A bat flies at a steady speed of 4 ms-1 emitting a sound of f =90 x 103 Hz. It is flying horizontally towards a vertical wall. The frequency of the reflected sound as detected by the bat will be (take velocity of sound in air is 330 ms-1)
88.1 × 103 Hz
87.1 × 103 Hz
92.1 × 103 Hz
89.1 × 103 Hz
A closed organ pipe and an open organ pipe of same length produce 2 beats/second while vibrating in their fundamental modes. The length of the open organ pipe is halved and that of closed pipe is doubled. Then the number of beats produced per second while vibrating in the fundamental mode is
2
6
8
7
A uruform wire of length L, diameter D and density ρ is stretched under a tension T. The correct relation between its fundamental frequency f, the length L and the diameter D is
Three liquids of equal masses are taken in three identical cubical vessels A, B and C. Their densities are ρA, ρB and ρC respectively but ρA < ρB < ρC . The force exerted by the liquid on the base of the cubical vessel is
maximum in vessel C
minimum in vessel C
the same in all the vessels
maximum in vessel A
Water is in streamline flows along a horizontal pipe with non-uniform cross-section. At a point in the pipe where the area of cross-section is 10 cm2, the velocity of wateris 1 ms-1 and the pressure is 2000 Pa. The pressure at another point where the cross-sectional area is 5 cm2 is
4000 Pa
2000 Pa
1000 Pa
500 Pa
The temperature of a gas contained in a closed vessel of constant volume increases by 1°C when the pressure of the gas is increased by 1%. The initial temperature of the gas is
100 K
273°C
100°C
200 K
Two slabs are of the thicknesses d1 and d2. Their thermal conductivities are K1 and K2 respectively. They are in series. The free ends of the combination of these two slabs are kept at temperatures θ1 and θ2. Assume θ1 > θ2. The temperature θ of their common junction is
Hot water cools from 60°C to 50°C in the first 10 min and to 42°C in the next 10 min. Then the temperature of the surroundings is
20°C
30°C
15°C
10°C
The efficiency of Carnot's heat engine is 0.5 when the temperature of the source is T1 and that of sink is T2. The efficiency of another Carnot's heat engine is also 0.5. The temperatures of source and sink of the second engine are respectively
2T1, 2T2
T1 + 5, T2 − 5
T1 + 10, T2 − 10
A.
2T1, 2T2
Efficiency of Carnot's heat engine,
Efficiency remains same when both T1 and T2 are increased by same factor.