Where is this physics equation derived from?

[sanguinee]

For an AAMC question: "round-trip time t for a ball thrown vertically is given by t=2v/g"

Where is this formula derived from? I thought it was from one of the three equations but couldn't derive it. Should I memorize it as an important formula? I usually use the x=vot+... formula and set vo=0, but this is the first time i'm coming across this formula. thank you!

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[Cawolf]

Vz = Vz0 + at

We want to know when the ball reaches the top of the parabola, or when Vz = 0.

0 = Vz0 + at

Vz0 = -at = -(-g)t = gt

t = Vz0/g

This is half the time for a parabolic trip, so just multiply it by 2 for the total time.

total t = 2Vz0/g

 

[sanguinee]

@Cawolf you're amazing - thank you!