Question

A jet air plane travelling at a speed of 500 km/h ejects its products of combustion at a speed of 1500km/h relative to the jet plane. The speed of the latter with respect to an observer on the ground is:-

• A. $1500km/h$
• B. $2000km/h$
• C. $1000km/h$
• D. $500km/h$

Answer 1

The correct option is C $1000km/h$

$v_{jet}=500km/h$

Speed of the products of combustion with respect to the jet plane$={v^{\prime }}_{smoke}=-1500km/h$

$v_{smoke}={v^{\prime }}_{smoke}-v_{jet}⟹-1500={v^{\prime }}_{smoke}-500\therefore {v^{\prime }}_{smoke}=-1000km/h$