What would be the effect of dropping a penny onto someone's head from the top of the tallest building?
Dropping a penny from the tallest building would have little effect if it hit someone.
If you drop an object off a tall building it accelerates under gravity increasing speed. It will also experience air resistance which slows it down. The speed when gravity and air resistance balance out is called the terminal velocity.
The terminal velocity of a penny is about 15m/s. This is quite slow. If the penny were to hit someone on the head, it might hurt a bit, but it wouldn't do any damage.
In fact tall buildings have really complex wind systems. If you were to drop a penny from the top of a skyscraper, it would probably get caught in a wind system and could end up a long distance away.
In fact it would be almost impossible to drop a penny onto someone's head from the top of a tall building.