11.

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 $\mathrm{S} = \frac{1}{3} {\mathrm{t}}^2$, where t is in second. Work done by the force in 2 is

• $\frac{8}{3} \mathrm{J}$

• $\frac{19}{5} \mathrm{J}$

• $\frac{5}{19} \mathrm{J}$

• $\frac{3}{8} \mathrm{J}$

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

• $\frac{1}{8\mathrm{\pi }}\sqrt{{\mathrm{k}}_1 + {\mathrm{k}}_2}$

• $8\mathrm{\pi } \sqrt{\frac{{\mathrm{k}}_1 + {\mathrm{k}}_2}{{\mathrm{k}}_1{\mathrm{k}}_2}}$

• $\frac{\mathrm{\pi }}{2}\sqrt{{\mathrm{k}}_1 - {\mathrm{k}}_2}$

• $\frac{\mathrm{\pi }}{2}\sqrt{\frac{{\mathrm{k}}_1}{{\mathrm{k}}_2}}$

The equation of a progressive wave can be given by y = 15 sin (660 − 0.02 $\mathrm{\pi }$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$\sqrt{5}$ s. If velocity of sound in air is 300 ms^-1 the elevation of aircraft is

• 250 m

• $250\sqrt{5} \mathrm{m}$

• 1250 m

• 2500 m

Two tuning forks of frequency n₁ and n₂ produces n beats per second. If n₁ and n₂ are known, n₁ may be given by

• $\frac{{\mathrm{n}}_2}{\mathrm{n}} + {\mathrm{n}}_2$

• n₂n

• n₂ ± n

• $\frac{{\mathrm{n}}_2}{\mathrm{n}} - {\mathrm{n}}_2$

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