First convert km/hr to m/sec.
100 km/hr = 100 x 1000 x 1/3600 =27.8 m/sec
Distance covered by helicopter in 20 sec:
s=vt, Where s is the distance, v is the speed and t is the time.
Put values
s=27.8 x 20
s=556 meters
Now to find the height, we use tangent ratio.
Let the height=h
tan ∅= Opposite/ Adjacent
Put values
tan60= h/556
Multiply both sides by 556.
556 x tan 60 = h
or
h= 556 x tan 60
h= 963 meters
The helicopter is 963 feet above the ground.
Answer: 963 ft
