Apparent frequency of sound of engine is changing in the ratio 5/3 under the condition that engine is first aprroaching and then receding away from the observer. If velocity of sound is 340 m/s, then velocity of engine is
340 m/s
170 m/s
85 m/s
310 m/s
n balls each of mass m and velocity v collide with a wall, assume that the collisions are perfectly elastic. The pressure exerted per second on the wall is
3 mnv
mnv
2mnv
none
Eight small drops, each of equal charges and radii are coalesce to form a big drop. The capacity of bigger drop in comparison to each smaller drop will be :
4 times
2 times
32 times
8 times
An organ pipe, opened at both ends, has fundamental frequency of 30 Hz. If one of its ends is closed, then fundamental frequency will be :
15 Hz
30 Hz
45 Hz
60 Hz
A body has initial temperature of 80°C. It cools by radiation process. In 5 minutes, it cools down to 64°C and in 10 minutes, it cools down to 52C. The temperature of surrounding is:
8°C
16C
32C
24C
D.
24C
From Newton's Law of cooling
= initial temperature of the object
= final temperature of the object
t = time
K = coefficient of thermal conductivity
= temperature of the surrounding
In the first case,
--------------- (1)
In the second case,
--------------(2)
From eqns (1) and (2),we get
By solving,we get
= 24C
The surface tension of the soap solution is T. The work done in forming a soap bubble of radius r, is :
A mixture of oxygen and hydrogen are filled in a vessel at a fixed temperature. The ratio of average kinetic energies of atoms of H2 and O2 is
1 : 16
1 : 8
1 : 12
1 : 1
An ice at -50°C is to be converted into vapour at 100°C. The heat required in this process is
1028 calorie
624 calorie
745 calorie
810 calorie
The speed of sound in a gas (=1.5) at 300 K is 340 m/s. The rms velocity of gas molecules will be
340 m/s
m/s
340 m/s
340 m/s
If 2 g mole of diatomic gas and 1 g mole of monoatomic gas are mixed together, then the ratio of specific heats of mixture is
1 : 24
1 : 58
1 : 46
1 : 60