An engine approaches a hill with a constant speed. When it is at a distance of 0.9 ~km , it blows a whistle whose echo is heard by the driver after 5 seconds. If the speed of sound in air is 330 ~m / s , then the speed of the engine is :

Step-by-step solution

Let after 5 ~sec engine at point C aligned & t = AB 330 + BC 330 & 5= 0.9 1000 330 + BC 330 & BC =750 ~m aligned Distance travelled by engine in 5 ~sec =900 ~m -750 ~m =150 ~m Therefore velocity of engine = 150 ~m 5 ~sec =30 ~m / s