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## Homework Statement

A cheetah can run at approximately 100km/hr and a gazelle at 80km/hr. If both animals are running at full speed, with the gazelle 70m ahead, how long before the cheetah catches its prey?

## Homework Equations

s=vt (no acceleration)

v = km/hr / 3.6 = m/s

## The Attempt at a Solution

I understand that this is relative motion. I've calculated that it takes the cheetah 2.52 s to run 70m and that during that 2.52 sec the gazelle would run an additional 55.9 m so that the total distance that the cheetah has to run is 125.9 meters. I've calculated that the time it takes for the cheetah to run this distance at constant speed is 4.53 s. I've redone this question about 10 times and can't figure out what I'm doing wrong. Can anyone please shed some light on what is probably a ridiculously easy question. Thank you.