Simple harmonic motion and waves MCQs
Matric · Physics (10th) · 6 questions
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10th class physics: Simple harmonic motion and waves
A body is in simple harmonic motion when its acceleration is proportional to its displacement from the mean position and always points back towards it (a ∝ −x). A mass on a spring and a simple pendulum (for small swings) are the standard examples. Learn the terms: amplitude is the greatest displacement, the time period T is the time for one complete vibration, and frequency f = 1/T is measured in hertz. For a pendulum, T = 2π√(l/g): a longer string swings more slowly, but the mass of the bob does not matter. Waves carry energy from place to place without carrying the medium along. In transverse waves the particles vibrate across the direction of travel (waves on a string, light); in longitudinal waves they vibrate along it (sound in air). Every wave obeys v = fλ, which is the formula behind most numerical MCQs in this chapter.
Questions with answers
Written by Parcha from the syllabus. Samples until a subject reviewer checks them; report anything wrong from the practice screen.
Q1 · Parcha original · Sample
The time period of a simple pendulum depends on:
- A. The mass of the bob
- B. The amplitude (for small swings)
- C. The length of the pendulum
- D. The material of the string
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Answer: C. The length of the pendulum
For small swings, T = 2π√(l/g): the period depends only on the length l and the acceleration due to gravity g, not on the mass of the bob or the amplitude.
Open this question on its own pageQ2 · Parcha original · Sample
The SI unit of frequency is the:
- A. Hertz
- B. Second
- C. Metre
- D. Newton
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Answer: A. Hertz
Frequency is the number of vibrations per second; 1 hertz (Hz) = 1 vibration per second = 1 s⁻¹. The second is the unit of the time period.
Q3 · Parcha original · Sample
In simple harmonic motion, the acceleration of the body is:
- A. Constant
- B. Directly proportional to displacement and opposite to it
- C. Inversely proportional to displacement
- D. Always zero
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Answer: B. Directly proportional to displacement and opposite to it
SHM is defined by a = −(constant) × x: acceleration is proportional to displacement from the mean position and always directed towards it. It is greatest at the extremes and zero at the mean position.
Q4 · Parcha original · Sample
Waves transfer:
- A. Matter only
- B. Both matter and energy
- C. Neither matter nor energy
- D. Energy, without carrying matter along
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Answer: D. Energy, without carrying matter along
In a wave, the particles of the medium only vibrate about their positions; it is the energy that travels onward. A floating leaf bobs up and down as water waves pass but does not travel with them.
Q5 · Parcha original · Sample
Sound waves travelling through air are:
- A. Transverse waves
- B. Electromagnetic waves
- C. Longitudinal waves
- D. Stationary waves
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Answer: C. Longitudinal waves
Air particles vibrate back and forth along the direction the sound travels, forming compressions and rarefactions: longitudinal waves. Sound needs a medium; electromagnetic waves do not.
Q6 · Parcha original · Sample
A wave has a frequency of 50 Hz and a wavelength of 2 m. Its speed is:
- A. 25 m/s
- B. 100 m/s
- C. 52 m/s
- D. 0.04 m/s
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Answer: B. 100 m/s
v = fλ = 50 × 2 = 100 m/s.