Question

The distance between the 5th and the 15th crest is 0.4 m. What is the wavelength of
sound?​

Answer 1

Explanation:

We know that the distance between two crest and trough is called wavelength of a wave. Distance between 5th and 15th crest will be 10 λ. So, So, the wavelength of the sound is 2 cm.

Answer 2

IIn this question, you need to verify if the body will still be mid air or reach the ground 3 seconds after the drop.

Using formula s = ut + 1/2 gt^2,

250 = 0*t + 1/2 * 9.8 * t^2

t = 7.14 secs

So the body will reach the ground 7.14 sec after when dropped from height of 250 m. So at 3 sec, it will still be in air.

Velocity after 3 seconds = u + gt = 0 + 9.8*3 = 29.4 m/s

So, K.E. after 3 sec will be: 1/2 * m * v^2