Asked by Chelsea Woodard

A ball is thrown upward into the air with a speed of 15m/s. At what times does the ball pass a point 8 meters above the person's hand?
8m=-0.5(9.8)(t)
t=1.8 seconds
Is that correct?

Answers

Answered by Steve
The ball's height is modeled by

h(t) = 15t - 4.9t^2

The ball will be 8m high twice: on the way up and on the way down. These times can be found by solving

15t - 4.9t^2 = 8

See
http://www.wolframalpha.com/input/?i=15t+-+4.9t%5E2+%3D+8


If you include the units in your equation, you will see that the right side is not in meters...
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