Question

if we throw a ball in a train it goes up , then train moves ahead with a fast speed so why it doesnt goes backwards

Answer 1

due to inertia of motion

Answer 2

actually it goes backword when seens from ground.when we throw ball in trai then we have non inertial frame of reference in this both we and ball experience a force in the apposite direction of motion of trai .hencr we both moved this same velocity that's why our relative speed become zero and we will not able to se ball moving in backward direction.