Question

A passenger in a train drops a ball from the window of a train running at an acceleration $a$. A pedestrian, on the ground by the side of the rails, observes the ball falling along:

• A. vertically downward with an acceleration $\sqrt{g^2+a^2}$
• B. vertically downward with an acceleration $\sqrt{g^2-a^2}$
• C. a parabola with an acceleration $\sqrt{g^2+a^2}$
• D. a parabola with an acceleration $g$

Answer 1

The correct option is C a parabola with an acceleration $\sqrt{g^2+a^2}$

When the ball just drops from the window of running train, two forces will accelerate the ball as observed by the pedestrian on the ground. One force is $ma$, acting towards the motion of train and other is gravitational force $mg$, acting downward.

Thus, the resultant acceleration will be $\sqrt{a^2+g^2}$ and the motion will be the simply parabolic motion as expected in a projectile motion.

Thus, option C will be correct.