Suppose a stick is struck against
Question: Suppose a stick is struck against a frying pan in vacuum. Will the frying pan vibrate? Will we be able to hear the sound? Explain. Solution: Yes, the frying pan will vibrate. Since, it is being hit by the stick but vibrations need a medium to travel and there is no medium in vacuum, so wecannot hear the vibrations produced....
Read More →We have learnt that vibration
Question: We have learnt that vibration is necessary for producing sound. Explain why the sound produced by every vibrating body cannot be heard by us. Solution: Since, range of frequency for every vibrating body is different. But we can hear the vibrations which lies between the range of frequencies from 20 Hz to 20000 Hz, so sound of every vibrating body cannot be heard by us....
Read More →Name two musical instruments
Question: Name two musical instruments which produce sound by vibrating strings. Solution: Guitar and sitar are the two musical instruments which produce the sound by vibrating strings....
Read More →When we hear a sound,
Question: When we hear a sound, does any part of our body vibrate? Name the part. Solution: Yes, It is the eardrum which vibrates and sends vibrations to the inner ear, when we hear any sound....
Read More →Boojho saw a cracker burst at night
Question: Boojho saw a cracker burst at night at a distance from his house. He heard the sound of the cracker a little later after seeing the cracker burst. Give reason for the delay in hearing the sound. Solution: The light travels faster than sound. So, the light from the cracker reaches faster than that of sound of the cracker. Speed of light in air = 3 x 108 m/s Speed of sound in air = 330 m/s...
Read More →The angles of a triangle are in AP, and the greatest angle is double the least.
Question: The angles of a triangle are in AP, and the greatest angle is double the least. Find all the angles in degrees and radians. Solution: Let a - d, a, a + d be the three angles of the triangle that form AP. Given that the greatest angle is double the least. Now, $a+d=2(a-d) 2 a-2 d=a+d a$ $=3 d \ldots . .(1)$ Now by angle sum property, $(a-d)+a+(a+d)=180^{\circ} 3 a=180^{\circ} a=60^{\circ}$ $\ldots \ldots$ (2) From (1) and (2), 3d $=60^{\circ} \mathrm{d}=20^{\circ}$ Now, the angles are, ...
Read More →Does any part of our body vibrate
Question: Does any part of our body vibrate when we speak? Name the part. Solution: Yes, while speaking the part which vibrates is called vocal cords. It is below the throat and creates vibrations while speaking....
Read More →Ultrasound has frequency of vibration
Question: Ultrasound has frequency of vibration (a) between 20 and 20000 Hz (b) below 20 Hz (c) above 20000 Hz (d) between 500 and 10000 Hz Solution: (c) Ultrasound has frequency of vibration above 20000 Hz....
Read More →Pitch of sound is determined by its
Question: Pitch of sound is determined by its (a) frequency (b) speed (c) amplitude (d) loudness Solution: (a) Pitch or shrillness is determined by the frequency of sound....
Read More →1 Hz is equal to
Question: 1 Hz is equal to (a) 1 vibration per minute (b) 10 vibrations per minute (c) 60 vibrations per minute (d) 600 vibrations per minute Solution: (c) 1 Hz = 1 vibration per second = 60 vibrations per minute...
Read More →The loudness of sound is determined by its
Question: The loudness of sound is determined by its (a) amplitude of vibration (b) ratio of amplitude and frequency of vibration (c) frequency of vibration (d) product of amplitude and frequency of vibration Solution: (a) Loudness of sound is determined by the amplitude of its vibrations....
Read More →Loudness of sound is measured
Question: Loudness of sound is measured in units of (a) decibel (dB) (b) hertz (Hz) (c) metre (m) (d) metre/second(m/s) Solution: (a) Unit of loudness of sound is decibel (dB)....
Read More →Express each of the following angles in degrees.
Question: Express each of the following angles in degrees. (i) $\frac{5 \pi}{12}$ (ii) $-\frac{18 \pi}{5}$ (iii) $\frac{5}{5}$ (iv) $-4$ Solution: (i) Formula : Angle in degrees $=$ Angle in degrees $\times \frac{\pi}{180}$ Therefore, Angle in degrees $=\frac{5 \pi}{12} \times \frac{180}{\pi}=75^{\circ}$ (ii) Formula : Angle in degrees $=$ Angle in radians $\times \frac{180}{\pi}$ Therefore, Angle in degrees $=-\frac{18 \pi}{5} \times \frac{180}{\pi}=-648^{\circ}$ The angle in minutes = Decimal ...
Read More →order to reduce the loudness of a sound,
Question: order to reduce the loudness of a sound, we have to (a) decrease its frequency of vibration of the sound (b) increase its frequency of vibration of the sound (c) decrease its amplitude of vibration of the sound (d) increase its amplitude of vibration of the sound Solution: (c)Since, loudness depends upon amplitude, so it can be increased by increasing amplitude and it can be decreased by decreasing amplitude....
Read More →Which of the following statements are correct?
Question: Which of the following statements are correct? (i) Sound is produced by vibrations. (ii)Sound requires a medium for propagation. (iii)Light and sound both require a medium for propagation. (iv)Sound travels slower than light. (a) (i) and (ii) (b) (i), (ii) and (iii) (c) (ii), (iii) and (iv) (d) (i), (ii) and (iv) Solution: (d) Because light can travel in vacuum also but it is only sound which requires medium to travel....
Read More →The loudness of sound depends on
Question: The loudness of sound depends on (a) its amplitude (b) its time period (c) its frequency (d) its speed Solution: (a) Sound will be loud when its amplitude is large and sound will be soft when its amplitude is small hence, loudness of sound depends upon its amplitude....
Read More →A list of mediums is given below
Question: A list of mediums is given below (i) Wood (ii) Water (iii) Air (iv) Vacuum In which of these mediums can sound travel? (a) (i) and (ii) (b) (i), (ii) and (iii) (c) (iii) and (iv) (d) (ii), (iii) and (iv) Solution: (b) Sound requires any medium to travel but in vacuum there is no medium, so sound cannot travel through them....
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians $-22^{\circ} 30^{\prime}$ Solution: Formula : Angle in radians = Angle in degrees $\times \frac{\pi}{180}$ The angle in radians $=\frac{\text { angle in minutes }}{60}$ Therefore, the total angle $=-\left(22+\frac{30}{60}\right)=-22.5$ Therefore, Angle in radians $=-22.5 \times \frac{\pi}{180}=-\frac{\pi}{8}$...
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians $-270^{\circ}$ Solution: Formula : Angle in radians = Angle in degrees $\times \frac{\pi}{180}$ Therefore, Angle in radians $=-270 \times \frac{\pi}{180}=-\frac{3 \pi}{2}$...
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians $7^{\circ} 30 .^{\prime}$ Solution: Formula: Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ The angle in radians $=\frac{\text { angle in minutes }}{60}$ Therefore, the total angle $=7+\frac{30}{60}=7.5$ Therefore, Angle in radians $=7.5 \times \frac{\pi}{180}=\frac{\pi}{24}$...
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians $400^{\circ}$ Solution: Formula : Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ Therefore, Angle in radians $=400 \times \frac{\pi}{180}=\frac{20 \pi}{9}$...
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians $330^{\circ}$ Solution: Formula: Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ Therefore, Angle in radians $=330 \times \frac{\pi}{180}=\frac{11 \pi}{6}$...
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians $225^{\circ}$ Solution: Formula : Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ Therefore, Angle in radians $=225 \times \frac{\pi}{180}=\frac{5 \pi}{4}$...
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians Solution: Formula : Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ Therefore, Angle in radians $=120 \times \frac{\pi}{180}=\frac{2 \pi}{3}$...
Read More →Express each of the following angles in radians
Question: Express each of the following angles in radians $36^{\circ}$ Solution: Formula : Angle in radians $=$ Angle in degrees $\times \frac{\pi}{180}$ Therefore, Angle in radians $=.36 \times \frac{\pi}{180}=\frac{\pi}{5}$...
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