Find speed in Km/Hr ?

Percy standing in the midst of a field observes a flying bird in his north at an angle of elevation of #30^@# and after #2min# he observes the bird in his south at an angle of elevation of #60^@#. If the birdflies in a straight line all along at a height of #50sqrt3m#, then find its speed in kilometer per hour.

Percy standing in the midst of a field observes a flying bird in his north at an angle of elevation of #30^@# and after #2min# he observes the bird in his south at an angle of elevation of #60^@#. If the birdflies in a straight line all along at a height of #50sqrt3m#, then find its speed in kilometer per hour.

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Dec 11, 2017

Answer:

#6color(white)(88)kmh^-1#

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From the diagram we need to find distance c. Using Pythagoras' theorem #c = sqrt(a^2+b^2)#. we first find a and b

#a=(50sqrt(3))/sin(30)=100sqrt(3)#

#b=(50sqrt(3))/sin(60)=(50sqrt(3))/(sqrt(3)/2)=100#

#c=sqrt((100sqrt(3))^2+(100)^2)#

#c=sqrt(40000)=200color(white)(88)#metres

#200m=200/1000=1/5 km#

#2min = 2/60=1/30 hrs#

Distance travelled/ time taken = speed

#:.#

#(1/5)/(1/30)=6# #kmh^-1#

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