A bullet emerge from a barrel of length 1.2 m with a speed of 640 ms-1 . Assuming constant acceleration, the approximate time that it spends in the barrel after the gun is fired is
4 ms
40 ms
400 μs
1 s
A body of mass 3 kg acted upon by a constant force is displaced by S' metre, given by relation , where t is in second. Work done by the force in 2 is
A beaker of radius 15 cm is filled with a liquid of surface tension 0.75 N/m. Force across an imaginary diameter on the surface of the liquid is
0.075 N
1.5 × 10-2 N
0.225 N
2.25 × 10-2 N
Two springs are joined and attached to a mass of 16 kg. The system is then suspended vertically from a rigid support. The spring constant of the two springs are k1 and k2 respectively. The period of vertical oscillations of the system will be
The equation of a progressive wave can be given by y = 15 sin (660 − 0.02 x) cm. The frequency of the wave is
330 Hz
342 Hz
365 Hz
660 Hz
A hollow cylinder with both sides open generates a frequency f in air. When the cylinder vertically immersed into water by half its length the frequency will be
f
2f
f/2
f/4
Two stretched strings have lengths land 2l while tension are T and 4 T respectively. If they are made of same material the ratio of their frequency is
2 : 1
1 : 2
1 : 1
1 : 4
When sound is produced in an aeroplane moving with a velocity of 200 m/s horizontal its echo is heard after 10 s. If velocity of sound in air is 300 ms-1 the elevation of aircraft is
250 m
1250 m
2500 m
D.
2500 m
From the figure for sound travel ABC
Given,
Time for the echo = s
Velocity of the plane = 200 m/s
Here, OC = 200 x = 2236 m
BC = velocity of sound x
⇒ BC = 300 × = 3354 m
OB =
= 2500 m
The plane is 2500 m above the ground.
Two tuning forks of frequency n1 and n2 produces n beats per second. If n1 and n2 are known, n1 may be given by
n2n
n2 ± n
A car moving with a velocity of 36 km/h crosses a siren of frequency 500 Hz. The apparent frequency of siren after passing it will be
520 Hz
485 Hz
540 Hz
460 Hz