A marble rolls off a coffee table at 0.8 m/s and lands. The same marble, launched from a kitchen counter at the same 0.8 m/s, lands too. Same marble, same launch speed, one difference: the counter is higher. Which flight lasts longer?
The flight ends when the marble reaches the floor. So look at the direction that ends it: the vertical one.
The flight lasts exactly as long as the fall. The marble stays in the air until it has fallen the whole launch height.
Both falls are the same free fall, starting from zero vertical velocity. From the counter there is more height to fall, and the same free fall takes longer to cover more height.
The launch speed was the same for both launches, and it is sideways motion anyway. The fall alone decides the flight time.
A toy car rolls off a low shelf, then off a higher shelf at the same speed. Compare the second flight's time in the air.
A ball bearing is launched horizontally at the same speed from a window ledge and from a higher window ledge. Why does the higher launch spend more time in the air?
The same pebble is launched horizontally at the same speed from a porch rail and from a rooftop. Which flight lasts longer?
The flight lasts as long as the fall.
Both falls are the same free fall from zero vertical velocity.
The rooftop launch has more height to fall, and the same free fall takes longer to cover more height.
The rooftop flight lasts longer, because its fall is longer.
Two identical marbles are launched horizontally at the same speed and instant, one from a step stool and one from a ladder top. Where is the ladder marble when the step-stool marble lands?
Three identical balls roll off a low porch step, a higher deck railing, and a still higher balcony railing at the same speed and the same instant. Which ball lands first?
A phone slides off a desk as an identical phone slides off a taller dresser at the same speed. Why is the dresser phone's flight longer?
Three identical quarters are knocked horizontally off shelves at the same instant: one from a 1 m shelf at 2 m/s, one from a 2 m shelf at 2 m/s, and one from a 1 m shelf at 4 m/s. Which quarter is in the air longest?