- #1

negation

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## Homework Statement

A book is toss into your dorm room, just clearing a windowsill 4.2m above ground.

a)If the book leaves your hand 1.5m above ground, how fast must it be going to clear the sill?

b)How long after it leaves your hand will it hit the floor, 0.87m below the windowsill?

## Homework Equations

none.

## The Attempt at a Solution

a)vf^2 - vi^2 = 2g(yf - yi)

-vi^2 = 2(-9.8ms^-2) (4.2m-1.5m)

vi = 7.274613392ms^-1

b)vi = 7.274613392ms^-1

yf - yi = 4.2m - 1.5m (are the directions correct?)

g = -9.81ms^-2

yf - yi = vit + 0.5gt^2

3.33m - 1.5m = 7.274613392ms^-1 t - 4.905 ms^-2 t^2

solving via quadratic equation:

t = 1.162s && t = 0.32

Which t do I take? Conceptual explanation please?

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