Question

A jet airplane travelling from east to west at a speed of 500kmh−1 ejected out gases of combustion at a speed of 1500kmh−1 with respect to the jet plane. What is the

A jet airplane travelling from east to west at a speed of ( 500 mathrm{km} mathrm{h}^{-1} ) ejected out gases of combustion at a speed of ( 1500 mathrm{km} mathrm{h}^{-1} ) with respect to the jet plane. What is the velocity of the gases with respect to an observer on the ground?
(A) ( 1000 mathrm{km} mathrm{h}^{-1} ) in the direction west to east
(B) ( 1000 mathrm{km} mathrm{h}^{-1} ) in the direction east to west
(C) ( 2000 mathrm{km} mathrm{h}^{-1} ) in the direction west to east
(D) ( 2000 mathrm{km} mathrm{h}^{-1} ) in the direction east to west

JEE/Engineering Exams

Physics

Solution

158

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Velocity of jet w.r.t. ground ( mathbf{V}_{mathrm{jg}}=500 mathrm{km} / mathrm{h} )
(Upward) Velocity of products relative to jet ( mathbf{V}_{mathrm{P} mathrm{J}}=1500 ) ( mathrm{km} / mathrm{h} )
Hence, velocity of products relative to ground = ( -1500+500 )
[
=
]
( -1000 mathrm{km} / mathrm{h} )
Here - ve sing means downward.