Posted by **Melissa** on Sunday, September 19, 2010 at 2:49pm.

A child throws a ball with an initial speed of 8 m/s at an angle of 40 degrees above the horizontal. The ball leaves her hand 1 m above the ground. How long is the ball in flight before it hits the ground? What is the magnitude of the ball's velocity just before it hits the ground? At what angle below the horizontal does the ball approach the ground?

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**Damon**, Sunday, September 19, 2010 at 3:07pm
it falls

initial speed up = Vi = 8 sin 40

y = yo + Vi t -4.9 t^2

0 = 1 + 8 sin 40 t -4.9 t^2

solve for t, time to hit ground

horizontal velocity u = 8 cos 40 forever

find v at t = time to hit ground

v = Vi -9.8 t (will be negative, down)

tan angle = v/u

magnitude speed = sqrt(u^2+v^2)

- physics -
**Melissa**, Sunday, September 19, 2010 at 3:33pm
When it says magnitude of velocity is that the same as the final velocity before impact? The word "magnitude" threw me off.

- physics -
**Damon**, Sunday, September 19, 2010 at 5:21pm
magnitude is the size sqrt (u^2+v^2)

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