SolveItClass 9 · NCERT

NCERT Solutions · Class 9 Science Sound Waves: Characteristics and Applications

28 questions · 16 still being checked

Pause and Ponder 10.1–10.2 (part 2 of 21)

  1. Exercise 10.1

    Explore various ways of producing sound.

    Not cross-checked

    NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.

    Sound is produced whenever something vibrates — every method below is just a different way of setting an object vibrating.
    NCERT_Solution_Class9_Science_Ch10_PP_Q10-1
    Plucking a stretched band or string — stretch a rubber band across an open cardboard box and pluck it (Activity $\displaystyle 10.1$); the band is seen vibrating, and the moment the vibration stops, so does the sound.
    Striking a metal object — a taal or any sonorous metal rings when struck.
    Blowing across an air column — in a bansuri the air inside the hollow pipe vibrates.
    Striking a tuning fork on a rubber pad — the prongs vibrate; touch a prong to water and ripples spread out, proving the vibration (Activity $\displaystyle 10.2$).
    Using the vocal cords — talking or singing vibrates the stretched flaps in the larynx; touch your throat while you speak and feel it.
    Rubbing body parts — grasshoppers and crickets rub their wings or legs together.
    Knocking, scratching or tapping — knock a desk (Activity $\displaystyle 10.3$), or tap two spoons together in air and again under water (Activity $\displaystyle 10.4$).
    Rapid expansion of heated gas — a firecracker or a clap of thunder heats gas so fast that the sudden density disturbance is heard as a loud pulse.
    Common thread: in every case the vibrating object is the source, and the sound ends when the vibration ends.

  2. Exercise 10.2

    Make a list of different types of musical instruments and identify their vibrating parts which produce sound. Threads of Curiosity What if your name were a tune instead of a word? In Kongthong, a village near Shillong in Meghalaya also known as the Whistling Village every person has a ‘tune name’ that can be sung or whistled. This unique tradition, called Jingrwai Iawbei, begins at birth when a mother composes a lullaby-like tune for her child. Let your friend gently knock or scratch on the desk. Listen carefully to the sound produced with your ear in the air.

    Not cross-checked

    NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.

    Every instrument sounds because some part of it vibrates — the instruments named in this chapter, with that part, are:
    NCERT_Solution_Class9_Science_Ch10_PP_Q10-2
    Bansuri (flute) — the air column inside the hollow pipe, set vibrating by blowing.
    Tabla and mridangam — the stretched membrane of the drum head, whose vibration is shaped by the black syaahi patch at its centre.
    Sitar, sarangi, veena, tanpura, ektara — the stretched strings; the sitar, sarangi and veena add extra strings to enrich the sound.
    Taal — the metal discs themselves, which ring when struck because metals are sonorous.
    Tuning fork — the two prongs (tines) of the U, struck against a rubber pad.
    Rubber band stretched on an open box — the band, the simplest instrument you can make yourself.
    Most instruments have more than one vibrating part — a plucked string also sets the body and the air inside it vibrating.
    That is why a flute, an ektara and a tabla playing the same note at the same loudness still sound different: their timbre comes from the pattern of overtones their shape and material produce.