hi. i have this projectile problem and i cant seem to get this one question right.(adsbygoogle = window.adsbygoogle || []).push({});

A ball is thrown with an initial speed of 30 m/s at an angle of 45°.The ball is thrown from a height of 11 m and lands on the ground.

i know the equation i have to use is:

Yf = Yo + Vot - (1/2)gt^2

i know my Vo = 30sin45 = 21.213 m/s

g = -9.81

i know the given Y is 11 m but im really confused about what should be my Yf and Yo. Most importantly, how can I manipulate the equation to find t??

what i thought it could be is like this...but i know its not right:

0 = 11 + (21.213)t - (.5)(-9.81)t^2

-11 = 21.213t - 4.905t^2

and thats about the farthest i could get...which isnt very far

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# Homework Help: Projectile motion at top of cliff with angle

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