# Mini-Quiz: Gravity Time Equations for Objects Projected Downward

by Ron Kurtus (revised 7 January 2011)

Take this Mini-Quiz to check your understanding of the lesson material.

1. How long does it take to reach 118 m/s if the initial velocity downward is
20 m/s?

1 second

9.8 seconds

10 seconds

2. If t = [−vi + √(vi2 + 2gy)]/g, how long does it take to reach 64 ft if the initial velocity is +32 ft/s?

t = [−32 + √(322 + 2*32*64)]/32 seconds

t = [−32 + √(322 + 2*9.8*64)]/9.8 seconds

t = [32 + √(322 + 2*32*64)]/32 seconds

3. What is the time when the displacement is zero?

t = [−vi + √(vi2 )]/g = 2vi/g seconds

t = [−vi + √(vi2 )]/g = 0 seconds

y cannot equal zero

If you got all three correct, you are on your way to becoming a Champion in Physics. If you had problems, you had better look over the material again.

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