# Think Fast

One day I decide I want to see how high I can throw a rock. I throw a rock straight up in the air and it has a speed of $30~\mbox{m/s}$ when it leaves my hand. I then realize this was foolish, as I need to get out of the way before the rock comes back down and hits me on the head. How many seconds do I have to move out of the way after I throw the rock?

Details and assumptions

• The acceleration of gravity is $-9.8~\mbox{m/s}^2$.
• Treat me as a point mass.
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