VITEEE 2018 :: Physics :: General questions

• Physics - General questions

 In Young's double slit experiment intensity at a point is (1/4) of the maximum intensity. Angular position of this point is (separation between slits is d)

Answer:

Explanation:

If a is the amplitude of the wave then

$\frac{I_{max}}{4}$ = a² = a² +a² +2aa cosΦ

or cos Φ = - 1/2 or Φ = 2π/3

Corresponding path difference,

Δx = $\frac{\phi\times\lambda}{2\pi}$ = $\frac{(2\pi/3)\times\lambda}{2\pi}$= λ/3

So, $d\sin\theta=\frac{\lambda}{3}$

or θ = $\sin^{-1}(\frac{\lambda}{3d})$ 

Two coils have a mutual inductance 0.005 H. The current changes in the first coil according to equation I = I₀ sin ωt, where I₀ = 10A and ω: 100 π radian/sec. The maximum value of e.m.f in the second coil is

Answer:

Explanation:

$e = M\frac{di}{dt} = 0.005\frac{d}{dt}(I_{0}\sin\omega t)$

$0.0005(I_{0}\omega\cos\omega t)$

= $\therefore e_{max}=0.005\times10\times100\pi=5\pi [ cos\omega t=1]$

The equivalent capacitance between a and b for the combination of capacitors shown in figure where all capacitances are in microfarad is 

Answer:

Explanation:

Rearranging the circuits, we get the following circuit.

.'. equivalent capacitance between A and B

C_AB = $\frac{4\times4}{4+4} = 2\mu F$

and equivalent capacitance between C and D,

C_CD = $\frac{8\times8}{8+8} = 4\mu F$

C _ab= 2μF+4μF = 6μF

The activity of a radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes. The decay constant is approximately

Answer:

Explanation:

$\frac{dN}{dt} = KN$

$9750 = KN_{0}$ .....(i)

975 = KN  .................(ii)

Dividing (i) by (ii)

$\frac{N}{N_{0}} = \frac{1}{10}$

$K=\frac{2.303}{t}\log{}{\frac{N_{0}}{N}}$

= $\frac{2.303}{5}\log{}{10}$ = 0.4606 =  0.461 per minute

A machine gun has a mass 5 kg. It fires 50 gram bullets at the rate of 30 bullets per minute at a speed of 400 m/s. What force is required to keep the gun in position?

Answer:

Explanation:

Force required = $\frac{Change in momentum}{time taken}$

= $\frac{(50\times10^{-3}\times30\times400-(5\times0)}{60}$ = 10 N

• Physics - General questions