When the frequency of the vibrating system becomes equal to the natural frequency of the system, this type of vibration is known as:

Which of the following are the basic differences between vibration signature and noise signature? 1. Vibration signature is essentially in the frequency range zero to 100 cps whereas noise signature is in the range 20 cps to 3000 cps. 2. Vibration signature has well-defined peaks whereas the noise signal is smeared. 3. The intensities of noise signatures arc much less than that of vibration signatures. 4. Detection of vibration signature calls for a microphone whereas that of noise can do with a pickup. Select the correct answer using the code given below.

A

1 and 4

B

2 and 3

C

1 and 2

D

3 and 4

Statement: Resonance is a special case of forced vibration in which the nature and frequency of vibration of the body are 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 the reason is the correct explanation of the statement

B

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

C

Statement is true, but the reason is false

D

Statement and reason are false

An undamped spring-mass system with mass m and spring stiffness k is shown in the figure. The natural frequency and natural period of this system are ω rad/s and T s, respectively. If the stiffness of the spring is doubled and the mass is halved, then the natural frequency and the natural period of the modified system, respectively, are

A

2ω rad/s and T/2 s

B

ω/2 rad/s and 2T s

C

4ω rad/s and T/4 s

D

ω rad/s and T s

A simple spring-mass vibrating system has a natural frequency of $${{\text{f}}_{\text{n}}}.$$ If the spring stiffness is halved and the mass is doubled, then the natural frequency will become

A

$$\frac{{{{\text{f}}_{\text{n}}}}}{2}$$

B

$$2{{\text{f}}_{\text{n}}}$$

C

$$4{{\text{f}}_{\text{n}}}$$

D

$$8{{\text{f}}_{\text{n}}}$$

In a vibrating reed type frequency meter, the reed which will vibrate the most is the one whose natural frequency is equal to

A

four times the frequency of supply

B

the frequency of supply

C

twice the frequency of supply

D

half the frequency of supply

A helical coil spring of stiffness k is cut to two equal halves and then these are connected in parallel to support a vibrating mass m. The angular frequency of vibration, ωn is

A

√k/m

B

√2k/m

C

√4k/m

D

√k/4m

There are four samples P, Q, R and S with natural frequencies 64, 96, 128 and 250 Hz respectively. They are mounted on test setups for conducting vibration experiments. If a loud pure note of frequency 144 Hz is produced by some instrument, which of the samples will show the most perceptible induced vibration?

A

P

B

Q

C

R

D

S

Vibrating screens are used for handling large tonnages of materials. The vibrating motion is imparted to the screening surface by means of

A

Electromagnets

B

Cams or eccentric shafts

C

Unblanced fly wheels

D

Either A, B or C

An organ pipe P1 closed at one end of vibrating in its first harmonic and another pipe P2 open at both ends vibrating in its third harmonic are in resonance with a given tuning fork. The ratio of the length of P1 to that of P2 is?

A

8/3

B

3/8

C

1/6

D

1/3

A machine mounted on a single coil spring has a period of free vibration of $${{\text{t}}_{\text{p}}}$$ . If the spring is cut into four equal parts and placed in parallel and the machine is mounted on them, then the period of free vibration of the new system will become

A

$$\frac{{{{\text{t}}_{\text{p}}}}}{{16}}$$

B

$$\frac{{{{\text{t}}_{\text{p}}}}}{4}$$

C

$$4{{\text{t}}_{\text{p}}}$$

D

$$16{{\text{t}}_{\text{p}}}$$

When the frequency of the vibrating system becomes equal to the natural frequency of the system, this type of vibration is known as:

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