Ayoung child standing in the aisle of a parked bus tosses a ball straight up in the air and lets it drop at her feet. if instead the bus is moving at a constant speed of 30 km/h straight down the street and the child tosses the ball up in the air and lets it drop, where will the ball land? why?

When the bus was at rest the ball landed at the child's feet.

Now, when the bus is moving at a constant velocity and the ball will again land at the child's feet

Reason:

The relative velocity of the child and the ball with respect of the bus is zero because they both are part of the same bus and are moving with the bus with same speed and in the same direction. Hence, There is no horizontal velocity of the ball with respect to the child. So, the ball will go vertically up with respect to the child and will land at the child's feet.

true tan speed = ang vel x radius