(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A ball is thrown straight upward from the ground with a speed of 30 m/s. What is the average speed of the ball in the first 5 seconds?

2. Relevant equations

VBy^{2}= VAy^{2}+ 2(ay) * dABy

VBy = VAy + ay * change in time

Average velocity = dABy / change in time

3. The attempt at a solution

VBy^{2}= VAy^{2}+ 2(ay) * dABy

(0)^{2}= (30)^{2}+ 2(9.8) * dABy

0 = 900 + 19.6 * daby

-900 = 19.6 *dABy

-45.9 = dABy

^but dABy can't be negative. what am i doing wrong?

also-- do i use "5 sec" for my time interval on the other equations? i cannot figure out what it means by "first 5 seconds." HELP

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# Homework Help: Speed of a ball

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