Question

A jet airplane travelling at the speed of 500 km h^–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 latter with respect to an observer on ground?

Answer 1

Speed of the jetairplane, v_jet = 500 km/h

Relative speed of itsproducts of combustion with respect to the plane,

v_smoke= – 1500 km/h

Speed of its productsof combustion with respect to the ground = v′_smoke

Relative speed of itsproducts of combustion with respect to the airplane,

v_smoke= v′_smoke– v_jet

– 1500 =v′_smoke –500

v′_smoke= – 1000 km/h

The negative signindicates that the direction of its products of combustion isopposite to the direction of motion of the jet airplane.