Question

A passenger rides on a train that is moving at 100.0 km/h eastward. The passenger walks toward the front of the train at a speed of 3 km/h relative to the train. Whilst walking, he throws a ball at 10 km/h toward the back of the train. What is the velocity of the ball relative to the ground?

Answer 1

velocity of train = 100 km/h (east)

Velocity of person walking in forward direction = 3 km/h (with respect to train)

now we can find the velocity of person with respect to ground as follows

$v_{pt} = v_p - v_t$

$v_p = v_{pt} + v_t$

$v_p = 100 + 3 = 103 km/h$

now he throw a ball backwards with speed 10 km/h with respect to him

so here we will have

$v_{bp} = v_b - v_p$

$-10 km/s = v_b - 103 km/h$

$v_b = 103 - 10 = 93 km/h$ Towards East

so with respect to ground the ball speed is 93 km/h towards East