Question

The pitch of the whistle of an engine appears to drop to`(5/6)^"th"` of original value when it passes a stationary observer. If the speed of sound in air is 350 m/s then the speed of engine is ____________.

विकल्प

• 35 m/s

• 70 m/s

• 105 m/s

• 140 m/s

Answer 1

The pitch of the whistle of an engine appears to drop to`(5/6)^"th"` of original value when it passes a stationary observer. If the speed of sound in air is 350 m/s then the speed of engine is 70 m/s.

Explanation:

`"n'" = "n"("v"/("v" + "v"_s))`

`"n'"/"n" = ("v"/("v" + "v"_s))`

`5/6 = 350/(350 + "v"_s)`

`"v"_"s" = 70  "m/s"`