Question

A jet airplance travelling at the speed of ` 500 km ^(-1)` ejects its products of combustion at the speed of ` 1500 km h^(-1)` relative to the jet plane. What is the speed of the burnt gases with respect to observer on the ground ?
A. `-100` kmph
B. `-1000` kmph
C. `-10` kmph
D. `-11` kmph

Answer 1

Correct Answer - B
Velocity of jet aeroplane `=500hatj`
velocity of fuel w.r.t to plane `=-1500hatj`
`:. vec(v)_(f) -vec(v_(p))=-1500hatj , vec(v_(f))= vec(v_(p))-1500hatj`
`=500hatj-1500hatj=-1000hatj`
`:.` speed of fuel w.r.t to ground is `-1000 km//hr`