A stone of density 2000 kg m-3 completely immersed in a lake is allowed to sink from rest. If the effect of friction is neglected, then after 4 seconds, the stone will reach a depth of
78.4 m
39.2 m
19.6 m
9.8 m
If the average kinetic energy of a molecule of a hydrogen gas at 300 K is E, then the average kinetic energy of a molecule of a nitrogen gas at the same temperature is
7 E
E/14
E
E/7
When the voltage and current in a conductor are measured as (100 ± 4) V and (5 ± 0.2) A, then the percentage of error in the calculation of resistance is
8 %
4 %
20 %
10 %
The set of physical quantities among the following which are dimensionally different is
terminal velocity, drift velocity, critical velocity
potential energy, work done, kinetic energy
dipole moment, electric flux, electric field
distintegration constant, frequency, angular velocity
An aeroplane is flying with a uniform speed of 150 km h-1 along the circumference of a circle. The change in its velocity in half the revolution (in km h-1) is
150
100
200
300
In uniform circular motion, the centripetal acceleration is
towards the centre of the circular path and perpendicular to the instantaneous velocity
a constant acceleration
away from the centre of the circular path and perpendicular to the instantaneous velocity
a variable acceleration making 45° with the instantaneous velocity
A man rides a bicycle with a speed of 17.32 ms-1 East- West direction. If the rain falls vertically with a speed of 10 ms-1, then the direction in which he must hold his umbrella is
30° with the vertical towards East
60° with the vertical towards West
30° with the vertical towards West
60° with the vertical towards East
B.
60° with the vertical towards West
Speed of bicycle = 17.32 ms-1
Speed of rain = 10 ms-1
From figure,
A body is thrown up with a speed u, at an angle of projection θ. If the speed of the projectile becomes on reaching the maximum height, then the maximum vertical height attained by the projectile is
In the given diagram, if PQ = A, QR = B and RS = C, then PS equals
A − B + C
A + B − C
A + B + C
A − B − C