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## Homework Statement

A ball is projected upward at time = 0.0 s, from a point on a roof 10 m above the ground. The ball rises, then falls and strikes the ground. The initial velocity of the ball is 98.8 m/s Consider all quantities as positive in the upward direction. The average velocity of the ball, during the first 8.79s is closest to:

## Homework Equations

## The Attempt at a Solution

We know that our intial velocity = 98.8m/s , and out final velocity = 0m/s

they are asking for the average velocity of the ball during the first 8.79 seconds. So I first tested out the equations which included v

_{0},v

_{x}, t, and g.

What I tried doing at first was I tried to find the time it took for the ball to hit the ground.

so I used the formula x=xo+(v0x)t-1/2gt^2

=10+(98.8)t+1/2(-9.8)t^2

Used the quadratic formula to solve for t and got t = 0.0493s

Since the average velocity is x2-x1/t2-t1

I tried 98.8-0/0.0493-8.79 and got -11.30.

Im so confused can someone explain to me how to get the correct answer.

Which is +56 m/s