Physics, asked by AarushiVKamat, 3 months ago

Q.2 What is sound ? How it is produced ? [2]
Q.3 What is a transverse wave ? In which medium - solid, liquid or gas can it
be produced ? [2]
Q.4 State two properties of ultrasound that make it useful to us. [2]
Q.5 Flash of lightning reaches earlier than the sound of thunder.
Give reason. [2]
Q.6 The heart of a man beats 75 times a minute. What is its frequency and
time period?
.
PLS ITS URGENT

Answers

Answered by purnahjadeja

Answer:

sound is vibration of an object

Answered by nidhithanik

Answer:

Sound is caused due to vibrations of a body.

Question 2

The correct statement is :

(a) Sound and light both require medium for propagation.

(b) Sound can travel in vacuum, but light can not

(d) Sound and light both can travel in vacuum.

Solution 2

Sound needs medium, but light does not need medium for its propagation.

Question 3

The heart of a man beats 75 times a minute.

What is its (a) frequency and (b) time period?

Solution 3

Given, heart beats 75 times a minute

(a) Frequency = No. of times heart beats in 1 s

Or, = 75/60 = 1.25 s-1

(b) Time period, T = 1/

Or, T = 1 / 1.25 = 0.8 s

Question 4

What is sound? How is it produced?

Solution 4

Sound is a form of energy that produces the sensation of hearing in our ears. Sound is produced by a vibrating body.

Question 5

The speed of sound in air at 0 C is nearly:

(a) 1450 m s-1 (b) 450 m s-1

Solution 5

330 m s-1

Question 6

The time period of a simple pendulum is 2 s. Find its frequency.

Solution 6

Frequency, = 1/T

Or, = 1/ 2 = 0.5 Hz

Question 7

Complete the following sentence:

Sound is produced by a ___________ body.

Solution 7

Vibrating

Question 8

Sound in air propagates in form of

(a) Longitudinal wave

(b) Transverse wave

(d) Neither longitudinal nor transverse wave.

Solution 8

Longitudinal wave

Question 9

The separation between two consecutive crests in a transverse wave is 100 m. If wave velocity is 20 m s-1, find the frequency of wave.

Solution 9

Given, wavelength = 100m

Wave velocity = 20 m/s

We know that,

Wave velocity = Frequency x Wavelength

Or, Frequency = Wave velocity / wavelength

Or, = 20/100 = 0.2 Hz

Question 10

Describe a simple experiment which demonstrates that the sound produced by a tuning fork is due to vibrations of its arms.

Solution 10

Experiment: A tuning fork is taken and its one arm is struck on a rubber pad and it is brought near a tennis ball suspended by a thread as shown in figure.

It is noticed that as the arm of the vibrating fork is brought close to the ball, it jumps back and forth and sound of the vibrating tuning fork is heard. When its arm stop vibrating, the ball becomes stationary and no sound is heard.

Question 11

The speed of light in air is :

(a) 3 x 108 m s-1 (b) 330 m s-1

Solution 11

3 x 108 m s-1

Question 12

A longitudinal wave travels at a speed of 0.3 m s-1 and the frequency of wave is 20 Hz. Find the separation between two consecutive compressions.

Solution 12

Wave velocity = 0.3 m/s

Frequency = 20 Hz

Separation between two consecutive compressions is the wavelength of a wave.

We know that,

Wave velocity = Frequency x Wavelength

Or, wavelength = Wave velocity / frequency

Or, = 0.3 / 20 = 1.5 x 10-2 m

Question 13

Describe in brief, with the aid of a sketch diagram, an experiment to demonstrate that a material medium is necessary for propagation of sound.

Solution 13

Experiment to demonstrate that a material medium is necessary for the propagation of sound:

An electric bell is suspended inside an airtight glass bell jar. The bell jar is connected to a vacuum pump as shown in figure. As the circuit of electric bell is completed by pressing the key, the hammer of the electric bell begins to strike the gong repeatedly due to which sound is heard.

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