# Multiple choice question for engineering

## Set 1

1. What is the principle of fibre optical communication?

a) Frequency modulation

b) Population inversion

c) Total internal reflection

d) Doppler Effect

### View Answer

2. What is the other name for maximum external incident angle?

a) Optical angle

b) Total internal reflection angle

c) Refraction angle

d) Wave guide acceptance angle

### View Answer

3. A single mode fibre has low intermodal dispersion than multimode. True or false?

a) True

b) False

### View Answer

4. How does the refractive index vary in Graded Index fibre?

a) Tangentially

b) Radially

c) Longitudinally

d) Transversely

### View Answer

5. Which of the following has more distortion?

a) Single step-index fibre

b) Graded index fibre

c) Multimode step-index fibre

d) Glass fibre

### View Answer

6. In which of the following there is no distortion?

a) Graded index fibre

b) Multimode step-index fibre

c) Single step-index fibre

d) Glass fibre

### View Answer

7. Which of the following loss occurs inside the fibre?

a) Radiative loss

b) Scattering

c) Absorption

d) Attenuation

### View Answer

8. What causes microscopic bend?

a) Uniform pressure

b) Non-uniform volume

c) Uniform volume

d) Non-uniform pressure

### View Answer

9. When more than one mode is propagating, how is it dispersed?

a) Dispersion

b) Inter-modal dispersion

c) Material dispersion

d) Waveguide dispersion

### View Answer

10. A fibre optic telephone transmission can handle more than thousands of voice channels. True or false?

a) True

b) False

### View Answer

11. Which of the following is known as fibre optic back bone?

a) Telecommunication

b) Cable television

c) Delay lines

d) Bus topology

### View Answer

12. Calculate the numerical aperture of an optical fibre whose core and cladding are made of materials of refractive index 1.6 and 1.5 respectively.

a) 0.55677

b) 55.77

c) 0.2458

d) 0.647852

### View Answer

^{2}-n2

^{2}) Numerical aperture = 0.55677

13. A step-index fibre has a numerical aperture of 0.26, a core refractive index of 1.5 and a core diameter of 100micrometer. Calculate the acceptance angle.

a) 1.47°

b) 15.07°

c) 2.18°

d) 24.15°

### View Answer

## Set 2

1. The mass of the moon is 1% of mass of the earth. The ratio of gravitational pull on moon and that of moon in earth will be

a) 1:1

b) 1:10

c) 1:100

d) 2:1

### View Answer

2. If the earth loses its gravity, then for a body

a) Weight becomes zero

b) Mass becomes zero

c) Neither mass nor weight is zero

d) Both mass and weight are zero

### View Answer

3. A ball is dropped from a spacecraft revolving around the earth at a height of 120km. What will happen to the ball?

a) It will go very far in the space

b) It will move with the same speed tangentially to the spacecraft

c) It will fall down to the earth gradually

d) It will continue to move with the same speed along the original orbit of the spacecraft

### View Answer

4. The velocity with which a projectile must be fired so that it escapes the earth’s gravitational field doesn’t depend on

a) Mass of the earth

b) Mass of the projectile

c) Radius of the orbit

d) Universal gravitational constant

### View Answer

5. The escape velocity of a projectile from the earth is approximately

a) 7km/sec

b) 11.2km.sec

c) 112km/sec

d) 1.1km/sec

### View Answer

_{e}=√2gR=11.2km/sec

6. The escape velocity of a body projected vertically upwards from the surface of the earth is 11km/sec. If the body is projected at an angle of 45° with the vertically, the escape velocity will be

a) 22km/sec

b) 11km/sec

c) 11√2km/sec

d) 11/√2km/sec

### View Answer

7. The escape velocity from the earth is 11.2km/sec. Another plant is having a mass 1000 times and radius 10 times that of the earth, then escape velocity at that planet will be

a) 11.2km/sec

b) 112km/sec

c) 1.12km/sec

d) 1120km/sec

### View Answer

_{e}=√(2GM/R)=11.2km/sec (v

_{e})

^{‘}=√((2G×100M)/(R/4))=2/9 √(2GM/R) (v

_{e})

^{‘}=2/9×11.2=2.5km/sec

8. Black hole is

a) Super surface of atmosphere

b) Ozone layer

c) Super dense planetary material

d) A hole on the surface of earth

### View Answer

9. If the orbital radius of the earth is made 4 times, then find the duration of the year if earlier it was T

a) T

b) 2T

c) 4T

d) 8T

### View Answer

_{2}/T

_{1}=(4r/r )

^{(3/2)}=(4)

^{(3/2)}=8 T

_{2}=8T

_{1}=8T

10. If radius of the earth is reduced, then

a) Time duration is reduced

b) Earth rotates slower

c) Time period of earth decreases

d) Duration of day increases

### View Answer

^{2}When R decreases, the moment of inertia decreases. But Iω=consatnt ω=2π/T increases Hence the period of rotation T decreases.

11. A point mass m is placed inside a spherical shell of radius R and mass M at a distance R/2 from the centre of the shell. The gravitational force exerted by the shell on the point mass is

a) GMm/R^{2}

b) GMm/R

c) Zero

d) 4GMm/R^{2}

### View Answer

12. A man is standing on an international space station which is orbiting earth at an altitude 520km with a constant speed 7.6km/s. If the man’s weight is 50kg, his acceleration is

a) 7.6 km/s^{2}

b) 7.6 m/s^{2}

c) 8.4 m/s^{2}

d) 10 m/s^{2}

### View Answer

_{h}=R

^{2}/(R+h)

^{2}g g

_{h}=(6400×10

^{3})

^{2}/[(6400+520)×10

^{3}]

^{2}×10=8.4m/s

^{2}

## Set 3

1. The circular motion of a particle whose speed is constant is

a) Periodic but not simple harmonic

b) Simple harmonic but not periodic

c) Periodic and simple harmonic

d) Neither periodic not simple harmonic

### View Answer

2. Which of the following is simple harmonic motion?

a) Particle moving in a circle with uniform speed

b) Wave moving through a string fixed at both ends

c) Earth spinning about its axis

d) Ball bouncing between two vertical walls

### View Answer

3. A particle executes simple harmonic motion along x-axis. The force acting on it is given by

a) Acos(kx)

b) Ae^{(-kx)}

c) Akx

d) –Akx

### View Answer

4. Which one of the following represents simple harmonic motion?

a) Acceleration = kx

b) Acceleration = k_{0} x+k_{1} x^{2}

c) Acceleration = -k(x+a)

d) Acceleration = k(x+a)

### View Answer

5. A particle executing simple harmonic motion of amplitude 5cm has maximum speed of 31.4 cm/s. The frequency of its oscillation is

a) 4Hz

b) 3Hz

c) 2Hz

d) 1Hz

### View Answer

_{max}=2πvA 31.4=2×3.14v×5 v=1Hz

6. A particle executes simple harmonic oscillation. Its amplitude is a. The period of oscillation is T. The minimum time taken by the particle to travel half of the amplitude from the equilibrium position is

a) T/8

b) T/12

c) T/2

d) T/4

### View Answer

7. A simple harmonic oscillator has an amplitude A and time period T. The time require by it to travel from x = A to x = A/2 is

a) T/6

b) T/4

c) T/3

d) T/2

### View Answer

8. If a simple harmonic oscillator has got a displacement of 0.02m and acceleration equal to 2m/s^{2} at any time, the angular frequency of the oscillator is equal to

a) 10 rad/s

b) 0.1 rad/s

c) 100 rad/s

d) 1 rad/s

### View Answer

^{2}y ω

^{2}=a/y=2/0.02=100 ω=10rad/s

9. The phase difference between acceleration of a particle executing simple harmonic motion and the instantaneous velocity is

a) π

b) 0.707π

c) Zero

d) 0.5π

### View Answer

10. Which one of the following statements is true for the speed v and the acceleration of a particle executing simple harmonic motion?

a) When c is maximum, a is maximum

b) Value of a is zero, whatever maybe the vale of v

c) When v is zero, a is zero

d) When v is maximum, a is zero

### View Answer

## Set 4

1. The motion of the earth about its axis is periodic and simple harmonic. True or false?

a) True

b) False

### View Answer

2. An object of mass 0.2kg executes simple harmonic motion along the x-axis with a frequency of (25/π)Hz. At the position x = 0.04, the object has kinetic energy of 0.5J and potential energy 0.4J. The amplitude of oscillation is

a) 6cm

b) 4cm

c) 8cm

d) 2cm

### View Answer

^{2}mv

^{2}A

^{2}0.5+0.4=2π

^{2}×0.2×(25/π)

^{2}A

^{2}A

^{2}=0.9/(0.4×25

^{2}) A=3/(2×25)=3/50 m=6cm

3. A spring of force constant 800N/m has an extension of 5cm. The work done in extending it from 5cm to 15cm is

a) 8J

b) 16J

c) 24J

d) 32J

### View Answer

_{1}= 5 cm, U

_{1}=1/2×k(x

_{1})

^{2}=1/2×800×0.05

^{2}=1J At x

_{2}=15cm, U

_{2}=1/2×k(x

_{2})

^{2}=1/2×800×0.15

^{2}=9J W=U

_{2}-U

_{1}=9-1=8J

4. A simple pendulum is attached to the roof of a lift. If time period of oscillation, when the lift is stationary is T, then frequency of oscillation when the lift falls freely, will be

a) Zero

b) T

c) 1/T

d) ∞

### View Answer

5. There is a simple pendulum hanging from the ceiling of a lift. When the lift is standstill, the time period of the pendulum is T. If the resultant acceleration becomes g/4, then the new time period of the pendulum is

a) 0.8T

b) 0.25T

c) 2T

d) 4T

### View Answer

^{‘}=2π×√((l/g)/4) T

^{‘}=2T

6. A lightly damped oscillator with a frequency v is set in motion by a harmonic driving force of frequency v’. When v’ is lesser than v, then response of the oscillator is controlled by

a) Spring constant

b) Inertia of the mass

c) Oscillator frequency

d) Damping coefficient

### View Answer

7. Statement: In simple harmonic motion, the velocity is maximum, when the acceleration is minimum [Reason:] Displacement and velocity in simple harmonic motion is differ in phase by π/2

a) Both statement and reason are true and reason is the correct explanation of the statement

b) Both statement and reason are true but reason is not the correct explanation of the statement

c) Statement is true, but reason is false

d) Statement and reason are false

### View Answer

8. What is time period of a pendulum hanged in a satellite? (T is the time period on earth)

a) Zero

b) T

c) Infinite

d) T/√6

### View Answer

9. Which of the following functions represents a simple harmonic oscillation?

a) sinωt-cosωt

b) sinωt+sin2ωt

c) sinωt-sin2ωt

d) sin^{2} ωt

### View Answer

^{2}y)/dt

^{2}=-ω

^{2}sinωt+ω

^{2}cosωt =-ω

^{2}(sinωt-cosωt) a=-ω

^{2}y that is a∝y This satisfies the condition of simple harmonic motion

10. The displacement of a simple harmonic motion doing oscillation when kinetic energy = potential energy (amplitude = 4cm) is

a) 2√2cm

b) 2cm

c) 1/√2 cm

d) √2 cm

### View Answer

## Set 5

1. The length of a simple pendulum executing simple harmonic motion is increased by 21%. The percentage increase in the time period of the pendulum of increases length is

a) 50%

b) 21%

c) 30%

d) 10.5%

### View Answer

2. A spring of spring constant 5×10^{3}N/m is stretched initially by 5cm from the unstretched position. Then the work done to stretch is further by another 5cmis

a) 6.25Nm

b) 12.50Nm

c) 18.75Nm

d) 25Nm

### View Answer

_{2})

^{2}-(x

_{1})

^{2}) W=1/2×5×10

^{3}×(0.10

^{2}-0.05

^{2}) W=18.75J

3. A particle is executing simple harmonic motion at midpoint of mean position and extremely. What is the potential energy in terms of total energy (E)?

a) E/4

b) E/16

c) E/2

d) E/8

### View Answer

^{2}Potential energy=1/2×k×A

^{2}/2

^{2}=1/4×1/2×k×A

^{2}=1/4×E

4. A mass m is suspended from a spring. Its frequency of oscillation is f. The spring is cut into two halves and the same mass is suspended from one of the two pieces of the spring. The frequency of oscillation of mass will be

a) √2 f

b) f/2

c) f

d) 2f

### View Answer

^{‘}=1/2π×√(2k/m)=√2 f

5. A particle executes simple harmonic motion with an amplitude a. The period of oscillation is T. The minimum time taken by the particle to travel half of the amplitude from the equilibrium position is

a) T/12

b) T/8

c) T/4

d) T/2

### View Answer

6. A particle executes simple harmonic motion with an angular velocity of 3.5 rad/sec and maximum velocity acceleration 7.5 m/s^{2} respectively. The amplitude of oscillations is

a) 0.28m

b) 0.36m

c) 0.707m

d) Zero

### View Answer

_{max}=ω

^{2}A A=a

_{max}/ω

^{2}=7.5/(3.5×3.5)=0.61m

7. The time period of a simple pendulum on a satellite, orbiting around the earth, is

a) Infinite

b) Zero

c) 84.6 min

d) 24 hours

### View Answer

8. A simple pendulum has a time period T. The pendulum is completely immersed in a non-viscous liquid, whose density is 1/10th of that of the material of the bob. The time period of the pendulum is immersed in the liquid is

a) T

b) T/10

c) √(9/10) T

d) √(10/9) T

### View Answer

_{0}=ρ/10, time period becomes T=2π√(l/(1-(ρ

_{0}/ρ) )g)=2π√(l/(9/10)g) T=√(10/9) T

9. Two bodies M and N of equal masses are suspended from separate massless spring of spring constants k_{1} and k_{2} respectively. If the two bodies oscillate vertically such that their maximum velocities are equal, the ratio of the amplitude of variation of M to that of N is

a) k_{1}/k_{2}

b) √(k_{1}/k_{2})

c) k_{2}/k_{1}

d) √(k_{2}/k_{1} )

### View Answer

_{max}(A)=v

_{max}(B) ω

_{1}A

_{1}=ω

_{2}A

_{2}√(k

_{1}/m)×A

_{1}=√(k

_{2}/m)×A

_{2}A

_{1}/A

_{2}=√(k

_{2}/k

_{1})

10. In forced oscillation of a particle, the amplitude is maximum for a frequency ω_{1} of the force, while the energy is maximum for a frequency ω_{2} of the force. Then

a) ω_{1}=ω_{2}

b) ω_{1} is lessed than ω_{2}

c) ω_{1} is lesser than ω_{2}, when damping is small and ω_{1} is greater than ω_{2}, when damping is large

d) ω_{1} is lesser than ω_{2}

### View Answer

_{1}=ω

_{2}

11. If a simple pendulum oscillates with amplitude of 50mm and time period of 2s, then its maximum velocity is

a) 0.10m/s

b) 0.16m/s

c) 0.24m/s

d) 0.32m/s

### View Answer

_{max}=ωA=2π/T×A v

_{max}=(2×3.14×0.05)/2=0.16m/s

12. If the period of oscillation of mass m suspended from a spring is 2s, then the period of mass 4m will be

a) 1s

b) 4s

c) 8s

d) 16s

### View Answer

_{2}/T

_{1}=√(m

_{2}/m

_{1})=√(4m/m)=2 T

_{2}=2T

_{1}=2×2=4s

13. Statement: Resonance is a special case of forced vibration in which the nature and frequency of vibration of the body is the same as the impressed frequency and the amplitude of forced vibration, is maximum [Reason:] The amplitude of forced vibrations of a body increases with an increase in the frequency of the externally impressed periodic force

a) Both statement and reason are true and reason is the correct explanation of the statement

b) Both statement and reason are true but reason is not the correct explanation of the statement

c) Statement is true, but reason is false

d) Statement and reason are false