A sound source producing waves of frequency 300 Hz and wavelength lm observer is stationary, while source is going away with the velocity 30 m is, then apparent frequency heared by the observer is

• 270 Hz

• 273 Hz

• 383 Hz

• 300Hz

172.

Linear density of a string of is 1.3 x 10^-4 kg/m and wave equation is y = 0.021 sin (x + 30t ), Find, the tension in the string where, x in metre and t in second

• 0.12 N

• 0.21 N

• 1.2 N

• 0.012 N

An observer is approaching with velocity v towards a light source. If the velocity of light is c, then velocity of light with respect to observer will be

• c - v

• c

• c + v

• $\sqrt{1 - \raisebox{1ex}{${\mathrm{v}}^2$}\!\left/ \!\raisebox{-1ex}{${\mathrm{c}}^2$}\right.}$

A 4 kg block is suspended from the ceiling of an elevator through a spring having a linear mass density of 19.2 x 10^-3 kg m^-3 . Find the speed with respect to spring with which a wave pulse can proceed on the spring if the elevator accelerates up at the rate of 2.0 ms^-2.
Take g = 10 ms^-2

• 30 m/s

• 42 m/s

• 46 m/s

• 50 m/s

Figure shows spring + block + pulley system which are light. The time period of mass would be

• $2\mathrm{\pi } \sqrt{\frac{\mathrm{k}}{\mathrm{m}}}$

• $\frac{1}{2\mathrm{\pi }}\sqrt{\frac{\mathrm{k}}{\mathrm{m}}}$

• $2\mathrm{\pi }\sqrt{\frac{\mathrm{m}}{\mathrm{k}}}$

• $\frac{1}{2\mathrm{\pi }} \sqrt{\frac{\mathrm{m}}{\mathrm{k}}}$

A bat emitting an ultrasonic wave of frequency 4.5 x 10' Hz at speed of 6 m/s between two parallel walls. The two frequencies heared by the bat will be

• 4.67 x 10⁴ Hz, 4.34 x 10⁴ Hz

• 4.34 x 10⁴ Hz, 4.67 x 10⁴ Hz

• 4.5 x 10⁴ Hz, 5.4 x 10⁴ Hz

• 4.67 x 10³ Hz, 4.34 x 10⁴ Hz

A wave packet with center frequency ω is propagating in dispersive medium with phase velocity of 1.5 x 10³ m/s. When the frequency ω is increased by 2%, the phase velocity is found to decrease by 3 %. What is group velocity of the wave packet?

• 0.25 × 10³ m/s

• 1.0 × 10³ m/s

• 0.6 × 10³ m/s

• 0.75 × 10³ m/s

When a stretched wire and a tuning fork are sounded together, 5  beats per second are produced, when length of wire is  95 cm or 100 cm, frequency of the fork is

• 90 Hz

• 100 Hz

• 105 Hz

• 195 Hz

Four massless springs whose force constants are 2k, 2k, k and 2k respectively are attached to a mass M kept on a frictionless plane as shown in the figure. If the mass M is displaced in the horizontal direction, then the frequency of the system is

The equation of a progressive wave is given by y = 5 sin$\left(100 \mathrm{\pi } \mathrm{t} - 0.4 \mathrm{\pi } \mathrm{x}\right)$ where y and x are in m and t is in s

(1) The amplitude of the wave is 5 m.

(2) The wavelength of the wave is 5 m.

(3) The frequency of the wave is 50 Hz.

(4) The velocity of the wave is 250 m s^-1

Which of the following statements are correct?

• (1), (2) and (3)

• (2) and (3)

• (1) and (4)

• All are correct