Alex is standing still and throws a football with a speed of 10 m/s to his friend, who is also standing still. The two friends are standing 5 meters apart.

Alex and his friend are both standing still, so they measure the football’s speed in the same reference frame. If air resistance is ignored, the football keeps its speed of 10 m/s as it travels the 5 meters, so both observe it moving at 10 m/s. The distance changes how long the throw takes, not its speed.

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