Question

A jet air plane traveling at a speed of $500km/hr$ ejects its products of combustion at the speed of $150km/hr$ relative to jet plane. What is the speed of combustion products w.r.t an observer on the ground?

Answer 1

Speed ​​of the jet airplane, $V_{jet}$ = 500 km / h.

Relative speed of its products of combustion with respect to the plane,

$V_{smoke}$ = - 1500 km / h

Speed ​​of its products of combustion with respect to the ground = $V_{smoke}$

Relative speed of its products of combustion with respect to the airplane,

$V_{smoke}$ = $V_{smoke}-V_{jet}$

- 1500 = $V_{smoke}$ - 500

$V_{smoke}$ = - 1000 km / h

The negative sign indicates that the direction of its products of combustion

is opposite to the direction of motion of the jet airplane.