An electric bulb marked as 50 W-200 V is connected across a 100 V supply. The present power of the bulb is
37.5 W
25 W
12.5 W
10 W
Three blocks of masses 4 kg, 2 kg, 1 kg respectively are in contact on a frictionless table as shown in the figure. If a force of 14 N is applied on the 4 kg block, the contact force between the 4 kg and the 2 kg block will be
2 N
6 N
8 N
14 N
In a mercury thermometer, the ice point (lower fixed point) is marked as 10° and the steam point (upper fixed point) is marked as 130°. At 40°C temperature, what will this thermometer read ?
78°
66°
62°
58°
Water is flowing through a very narrow tube. The velocity of water below which the flow remains a streamline flow is known as
relative velocity
terminal velocity
critical velocity
particle velocity
A train approaching a railway platform with a speed of 20 ms-1 starts blowing the whistle. Speed of sound in air is 340 ms-1. If the frequency of the emitted sound from the whistle is 640 Hz, the frequency of sound to a person standing on the platform will appear to be
600 Hz
640 Hz
680 Hz
720 Hz
C.
680 Hz
Given v = 340 ms-1, us = 20 ms-1 and v0 = 640 Hz
From Doppler's Law
What is the phase difference between two simple harmonic motions represented by and x2 = A cos (ωt) ?
Heat is produced at a rate given by H in a resistor when it is connected across a supply of voltage V. If now the resistance of the resistor is doubled and the supply voltage is made V/3, then the rate of production of heat in the resistor will be
H/18
H/9
6H
18H
When a spring is stretched by 10 cm, the potential energy stored is E. When the spring is stretched by 10 cm more, the potential energy stored in the spring becomes
2 E
4 E
6 E
10 E
The frequency of the first overtone of a closed pipe of length l1 is equal to that of the first overtone of an open pipe of length l2. The ratio of their lengths (l1 : l2) is
2 : 3
4 : 5
3 : 5
3 : 4
A body when fully immersed in a liquid of specific gravity 1.2 weighs 44 gwt. The same body when fully immersed in water weighs 50 gwt. The mass of the body is
36 g
48 g
64 g
80 g