On a long horizontally moving belt (Fig.3.26), a child runs to and fro with a speed `9 km h^(-1)` (with respect to the belt) between his father and mother located 50 m apart on the moving belt. The belt moves with a speed of `4 km h^(-1)`. For an observer on a stationary platform outside, what is the
(a) speed of the child running in the direction of motion of the belt ?
(b) speed of the child running opposite to the direction of motion of the belt ?
(c) time taken by the child in (a) and (b)?
Which of the anseres alter if motion is viewed by one of the parents ?

Options

A. `4 km h^(-1)`
B. `5 km h^(-1)`
C. `9 km h^(-1)`
D. `13 km h^(-1)`

Answer

D