A car moves from A to B with a speed of 30 km/h and from B to A with a speed of 20 km/h. What is the average speed of the car ?
25 km/h
24 km/h
50 km/h
10 km/h
A body starts from rest and moves with constant acceleration for t sec. It travels a distance x1 in first half of time and x2 in next half of time, then
x2 = x1
x2 = 2x1
x2 = 3x1
x2 = 4x1
What is the source temperature ofthe Carnot engine required to get 70% efficiency ? Given, sink temperature = 27°C.
1000°C
90°C
270°C
727°C
A 10 kg metal block is attached to a spring of spring constant 1000 Nm-1. A block is displaced from equilibrium position by 10 cm and released. The maximum acceleration of the block is
10 ms-2
100 ms-2
200 ms-2
0.1 ms-2
A metallic wire of 1 m length has a mass of 10 x 10-3 kg. If a tension of 100 N is applied to a wire, what is the speed of transverse wave ?
100 ms-1
10 ms-1
200 ms-1
0.1 ms-1
A trainis approaching towards a platform with a speed of 10 ms-1 while blowing a whistle of frequency 340 Hz. What is the frequency of whistle heard by a stationary observer on the platform ? Given speed of sound = 340 ms-1.
330 Hz
350 Hz
340 Hz
360 Hz
A flow of liquid is streamline, if the Reynold's number is
less than 1000
greater than 1000
between 2000 to 3000
between 4000 to 5000
A pipe of 30 cm long and open at both the ends produces harmonics. Which harmonic mode of pipe resonates a 1.1 kHz source? Given, speed of sound in air = 330 ms-1.
Fifth harmonic
Fourth harmonic
Third harmonic
Second harmonic
In anomalous expansion of water, at what temperature, the density of water is maximum ?
4°C
< 4°C
> 4°C
10°C
A cycle tyre bursts suddenly. What is the type of this process ?
Isothermal
Adiabatic
Isochoric
Isobaric
B.
Adiabatic
In a tyre burst there is too little time for the temperature to be equaized with the surroundings the work done due to the sudden expansion causes the air surrounding the tyre to get cooler. It is adiabatic, because no heat transfer occurs here most of the processes that take very little time is adiabatic.