Question

An aeroplane flying at a constant speed, parallel to the horizontal ground, 3 km above it, is observed at an elevation of 60 from a point on the ground. If, after five seconds, its elevation from the same point, is 30 , then the speed (in km/hr) of the aeroplane is

Answer 1

first see the diagram
I also give you answer without diagram but , by it it is so difficult to understand

Answer 2

Hello dear,

● Answer-
v = 1829 km/hr

● Explaination-
[Refer to the figure]

Looking at the figure,
sin60 = AB / OB
√3/2 = 3 / OB
OB = 2√3
OB = 3.46 km

Also,
sin30 = CD / OD
1/2 = 3 / OD
OD = 6 km

Distance travelled by aeroplane in 5 s -
s = OD - OB
s = 6 - 3.46
s = 2.54 km

Time taken is -
t = 5 s = 5/3600 hr

Speed of the aeroplane-
v = s / t
v = 2.54 / (5/3600)
v = 1829 km/hr

Therefore, speed of aeroplane is 1829 km/hr.

Hope it helps...