1.

A man jumps from a building with a source of sound. When he reaches halfway down, he starts the siren of frequency 100Hz. A person standing below him on the ground hears the first sound to be of frequency 120Hz. What is the height of the building? Speed of sound = 330m/s. Take g=9.81m/s^2.(a) 154m(b) 308m(c) 77m(d) 500mI got this question by my school principal while I was bunking the class.Asked question is from Waves in portion Waves of Physics – Class 11

Answer»

The correct CHOICE is (b) 308m

The best EXPLANATION: We can FIND the speed corresponding to the apparent FREQUENCY and then use that to find the height of the building.

120 = 100(330)/(330-v)v = 330 – 3300/12 = 55m/s.

Using, v^2 = 2gh, we can find the height covered by the man.The double of this value will be the height of the building as he is mid-way.

55^2 = 2*9.81*hh = 154mHeight of building = 2h = 308m.



Discussion

No Comment Found

Related InterviewSolutions