I've been trying to figure this question our for a while but for some reason I keep getting some stupid quadratic.
Robert flips a coin at a velocity of 3m/s and as it comes back, he fails to catch it resulting in it falling down an 8m deep well. How much time does it take for the coin to fall down the well.
Hey! So, if we ignore air resistance, the coin should move up and down in a perfect parabola. This means that, when it reaches the point at which it was originally flipped, it will be travelling at exactly 3m/s, but in the opposite direction! You can use formulas to prove this, but there really isn't any need; it's sort of intuitive.
Now, we can use the equation
to find the time! Just sub in 8m for delta y, 9.8 for a and 3m/s (initial velocity) for u. Solve the quadratic, and you're done!
Jake