Bright Tutorials Bright Tutorials
ICSE Class 10 Physics Question 12 of 20

Solved 2018 Question Paper ICSE Class 10 Physics — Question 9

Back to all questions
9
Question

Question 7(c)

A person is standing at the sea shore. An observer on the ship which is anchored in between a vertical cliff and the person on the shore fires a gun. The person on the shore hears two sounds, 2 seconds and 3 seconds after seeing the smoke of the fired gun. If the speed of sound in the air is 320 ms-1 then calculate: [4]

(i) the distance between the observer on the ship and the person on the shore.

(ii) the distance between the cliff and the observer on the ship.

A person is standing at the sea shore. An observer on the ship which is anchored in between a vertical cliff and the person on the shore fires a gun. The person on the shore hears two sounds, 2 seconds and 3 seconds after seeing the smoke of the fired gun. If the speed of sound in the air is 320 m/s then calculate: the distance between the observer on the ship and the person on the shore, the distance between the cliff and the observer on the ship. ICSE 2018 Physics Solved Question Paper.
Answer

Let d1 be the distance between the observer on ship and person on shore. The first sound heard by the person at shore after t1 = 2 s will be the direct sound of fire.

From relation v = dt\dfrac{d}{t},

320 = d12\dfrac{d_1}{2} or d1 = 640 m.

(ii) The second sound heard by the person at shore will be the echo heard after reflection from the cliff. Since, sound takes 2 s to reach from the observer to the person, so the time taken by the echo of fire to reach the observer will be t2 = 3 - 2 = 1 s.

Let d2 be the distance between the observer and the cliff. Then 2d2t2\dfrac{2d_2}{t_2} = v

Or d2 = vt22\dfrac{vt_2}{2} = 320×12\dfrac{320 \times 1}{2} = 160 m.