Q: Which coin will land first?

Answer:

Notice that all six coins have the same exact vertical motion. This is because all of them have the same initial vertical velocity of zero (and the acceleration of 9.81 m s^-2). Their horizontal motions however differ because they had different initial horizontal velocities.

Delving Deeper

Are you wondering why the horizontal spacing among the six coins look so evenly spaced out? Well, as the ruler swivels, different parts along the ruler travel at different speeds according to the formula v=rω. Because the coins were arranged evenly spaced out along the ruler, the ruler collided into them at speeds which are evenly spaced out. As a result, the (initial) momentum (and thus horizontal velocity) imparted to coins are also evenly spaced out.

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