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TYPES OF MOTION

CHAPTER-08
TYPES OF MOTION
Text Book Question and Answers
I. Four alternatives are gives to each of the incomplete statements/questions. Choose the correct answer.
1. Which of the following represent circular motion_________
a)ball sliding down an inclined plane. b)motion of a simple pendulum
c)A freely falling body d)A stone tied to a thread and whirled
Answer: d) A stone tied to a thread and whirled
2. The wave carries__________
a) Power b) energy c) displacement d) work
Answer: b) Engery
3. Which of the following is a longitudinal wave?
a)radio wave b)X-rays c)light waves d)sound waves.
Answer: d) Sound waves
4. The S.I unit of wavelength is__________
a)cm b)dm c)m d)km
Answer: c) m
5. The wavelength of a wave is 4 m and two waves per second passes a point, then the speed of the wave is_________
a)2 m/s b)8 m/s c)6 m/s d)4 m/s
Answer: b) 8 m/s
II. Complete the following statements
1. Waves are produced by periodic disturbance at a point in a medium(Vibration)
2. The speed of a wave depends on Nature of the medium
3. The distance between two consecutive compressions / rarefaction is wave length
4. The type of wave to which electromagnetic wave be longs to crests and troughs(transverse wave)
5. In a longitudinal wave, the vibration of particles, and the direction of wave are parallel

III. Match the following
1. Longitudinal wave – oscillation in spring.
2. Transverse wave – crests and troughs
3. Simple harmonic motion –oscillation of a simple pendulum

IV. Answer the following questions
1. Give the differences between a transverse wave and a longitudinal wave
Transverse waveLongitudinal wave
Particles vibrate in the direction perpendicular to the direction of wave propagationParticles vibrate along the direction of the propagation
The wave propagates in the form of crests and troughs.The wave propagates in the form of compressions and rarefactions
One crest and one trough constitute a waveOne compression and one rarefaction constitute a wave.
E.g.: Light waves, waves on surface of water, waves on a string etc.E.g.: Sound waves, Vibrations in gases, oscillations of spring etc.
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2. Does the particles of the medium in which a wave moves travel along with the wave? Explain wirh an example.
When a wave propagates in a medium the particles of the medium vibrate about their mean position and the energy is transferred without the transfer of the particles of the medium.
E.g.: take some water in a trough and float a piece of cork in it. By dipping your finger, disturb the water, the cork move up and down indicating the particles vibrate.
3. If we double the frequency of a vibrating object, what happens to its time period?
Time period= 1/n if n is doubled the time period T will be halved.
4. If the frequency of a transeverse wave is 10Hz. And the distance between the two consecutive wave crests is 2 m. calculate the wave speed.
n=10Hz l=2m
v=nl
v=10 x 2
v=20 m/s
5. Define simple harmonic motion and give two example of the same.
Simple harmonic motion is a type of periodic motion where the restoring force is directly proportional to the displacement
Or
Motion which repeats itself periodically is known as simple harmonic motion.
Or
The motion which repeats after regular interval of time, it is called simple harmonic motion.
Examples:
a. Oscillation of simple pendulum
b. When a tuning fork is hit against rubber pad, its prongs execute simple harmonic motion.
c. When the load attached to the lower end of a spring suspended from a support is pulled and released, it executes simple harmonic motion,
d. When the bus is in the clutch gear, we can see a vibration and hear the sound produced by it. This is simple harmonic motion.
6. Give two practical applications of simple harmonic motion.
a. Simple harmonic motion of a pendulum was used for the measurement of time.
b. Tuning the musical instrument is done with the vibrating tuning fork which executes simple harmonic motion.
c. Wave is a consequence of simple harmonic motion. Study of waves is indirectly the study of simple harmonic motion.
d. Molecules are in simple harmonic motion. This is studied with the help of vibration spectrum.

Additional Question and Answers
1. Define wave
Wave is a disturbance setup in a medium
Or
A wave is produced by the periodic disturbance at a point in a medium
Or
The disturbance produced in a medium by the to and fro motion of its particles about their mean position is called wave.
2. Define wave motion
The transference of energy, when the particles of a medium move about their mean position is called wave motion
Or
The disturbance that propagates in the medium is called wave motion.
3. Define wave velocity.
Velocity of the disturbance transmitted in a medium is called wave velocity.
Or
The distance travelled by a wave in one second is called wave velocity.
V=nl

V=wave velocity
n=frequency
l=wavelength
4. Define wavelength.
The linear distance covered by on complete wave is called wavelength. It is denoted by the symbol Greek letter lambda ‘l’
5. Define displacement.
The distance of the particle for its mean or equilibrium position is called displacement
6. Define amplitude.
The maximum displacement of a vibrating particle about its mean position is called amplitude.
7. Define oscillation. Give example
One complete to and fro motion of the particle its mean position is called Oscillation.
E.g. Motion of a swing.
8. Define time period.
Time taken by the body to complete one oscillation is called time period.
9. What is meant by periodic motion? Give an example.
A motion which repeats itself after a definite interval of time is called periodic motion.
Uniform circular motion of a particle is an example of periodic motion.
10. Define frequency.
The number of oscillations completed by the particle in one second is called frequency.
Or
The number of vibrations performed by a vibrating object per second is called its frequency.
Or
The number of waves that pass through a given point per second is called the frequency of the wave. It is also called wave number.
Or
For a particle executing simple harmonic motion, the number of cycles completed by the particle per second is called frequency.
S.I. unit of frequency is
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Hz(Hertz)
11. Define Simple harmonic motion.
An oscillatory motion under the influence of a restoring force which is proportional to and oppositely directed to the displacement from an equilibrium position is called simple harmonic motion.
12. Give three examples for imperceptible motions.
Examples of imperceptible motions include the following;
i) The molecules in a solid are in a state of continuous vibration. However, these vibrations are not visible to us.
ii) The continents are in a state of continuous drift. However, this motion is not recognized by our senses.
iii) The rotation and revolution of the earth is imperceptible to our senses.
13. List the important facts about wave motion of mechanical waves.
The following are some of the key facts about the wave motion of mechanical waves:
i) A mechanical wave is produced by a periodic disturbance at a point in the medium.
ii) Waves travel through a medium in the form of disturbances carrying energy along.
iii) The particles of the medium merely vibrate about their mean position and they are not carried along with the wave..
iv) The speed of a wave through a medium depends on the nature of the medium and not the energy content.
v) The relationship between wavelength (λ), frequency (n) and velocity (v) is given by the equation v = nλ
vi) The time-period (T) of a wave is equal to the reciprocal of its frequency (n). Thus, T=1/n
14. How are waves classified?
Waves are broadly classified into two types. They are mechanical waves and electromagnetic waves. Mechanical waves are further classified into two types. They are transverse waves and longitudinal waves. Electromagnetic waves are always transverse waves
15. Why sound is called a mechanical wave?
Sound requires a medium for its propagation. It propagates as an oscillation of matter and transfers energy through a medium. Hence it is called a mechanical wave.
16. Why is light called an electromagnetic wave?
A light of combined vibrations of electric field and magnetic field which travels through space carrying energy. It does not require a material medium for its propagation. Hence light is called an electromagnetic wave.
17. Distinguish between a mechanical wave and an electromagnetic wave
Mechanical wavesElectromagnetic waves
1. Mechanical waves require a material medium for their propagation.
2. Mechanical waves involve the vibration of particles of a medium.
1. Electromagnetic waves do not require a material medium for their propagation.
2. Electromagnetic waves involve combined vibrations of electric and magnetic fields.
18. What are transverse waves? Give two examples.
A wave is said to be transverse if the particles of the medium through which the wave travels vibrate at right angles to the direction of propagation of the wave.
E g. Water waves, Light waves, X-rays, Radio waves etc.
19. Why water waves are called transverse waves?
Water waves are known as transverse waves because the motion of the water is at right angles to the direction in which the waves travel. A cork placed in a tank carrying water waves in the form of concentric ripples merely moves up and down on water in its own position. This is perpendicular to the direction of propagation of ripples. This is why water waves are considered as transverse waves
20. What are longitudinal waves? Give two examples.
If the particles of a medium through which a wave is travelling vibrate in the direction of the wave itself back and forth, then, the wave is called a longitudinal wave.
E.g. Compressions and rarefactions produced in a slinky, sound waves etc.
21. What are crests and troughs, in relation to a transverse wave?
Crest: the uppermost part of wave i.e., the maximum displacement of the particles in upward direction is called crest
Trough: the maximum displacement of the particles in the downward direction is called trough
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22. What are compression and rarefaction, in relation to a longitudinal wave?
Compression: the region of the medium in which particles come to distance less than the normal distance between them is called compression.
Rarefaction: the region of the medium, in which particle of the medium get apart to distances greater than the normal distance between them is called rarefaction.
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23. What are mechanical waves? Give Examples.
The waves which require material medium for their propagation are called mechanical waves.
E.g. Waves produced in water in the form of concentric circles, sound, seismic waves etc.
24. What are electromagnetic waves? Give examples.
The waves associated with electric and magnetic fields, resulting from the acceleration of an electric charge are called Electromagnetic waves.
Examples: visible light, ultraviolet light, radio waves, X-rays etc.
25. Write the formula to find the time-period of a simple pendulum when its length is known. Explain the symbols used in the equation.
Time-period of a simple pendulum T = 2n root l/g
26. Name two basic characteristics of a simple harmonic motion.
Two basic characteristics of a simple harmonic motion are amplitude and frequency
27. List some of the characteristic properties of simple harmonic motion.
Some of the characteristic properties of simple harmonic motion include amplitude, oscillation, time-period and frequency.
28. Give examples of simple harmonic motion.
The following are some examples of simple harmonic motion:
1) The oscillations of a simple pendulum,
2) the swinging motion of the pendulum of a clock,
3) the motion of a swing,
4) uniform circular motion,
5) the motion of a prong of a vibrating tuning fork,
6) the vibration of molecules of a substance.
29. Give four applications of simple harmonic motion.
Following are some of the applications of simple harmonic motion:
i) The simple harmonic motion of a simple pendulum is used in the measurement of time.
ii) Tuning of musical instruments is done by employing the simple harmonic motion of a vibrating tuning fork.
iii) The motion of molecules is simple harmonic. This is studied using vibration spectrum. Production of a wave pattern is a consequence of simple harmonic motion. Study of waves is the study of simple harmonic motion.
30. What is the technique used to study the simple harmonic motion executed by the molecules of a substance?
The simple harmonic motion of the molecules of a substance is studied by using a technique called vibration spectrum
31. What is the relation between Time period (T) and the frequency (f) of the wave?
T=1/f or T=1/n
32. Frequency – waves per second (Hertz)
33. Amplitude - distance from reference point to peak or trough.
34. Wavelength – distance of one complete wave.
35. Period – time it takes for a wave to complete one cycle