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Throwing a dart from a roof  Velocity 
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#1
May810, 05:43 PM

P: 365

1. The problem statement, all variables and given/known data
A dart is thrown horizontally from a buildings rooftop. The dart's time of flight is 2.0 s. The dart sticks in the ground such that it makes a 53.1 degree angle with the ground. With what speed was the dart thrown? 3. The attempt at a solution I am studying for my final and i do not get this problem from one of my previous tests. The answer is 14.7 m/s and i have no idea how to get it. Can anyone point me in the right direction. Thank you :) 


#2
May810, 06:10 PM

HW Helper
P: 6,202

Well if it is throw horizontally, then the initial vertical velocity is zero right? Using an equation of motion, what would be final vertical velocity when t=2?



#3
May810, 06:36 PM

P: 365

Is the final vertical velocity when t=2 just 19.6 m/s
I got that from Vf = Vi + at oh so then from that the x component of the Vf will be the same as the velocity initial correct? so tan(53.1) = 19.6 / Vfx Vfx = 14.7 m/s Does that seem right? 


#4
May810, 06:44 PM

HW Helper
P: 6,202

Throwing a dart from a roof  Velocity
Yes that looks correct.



#5
May810, 06:48 PM

P: 365

Yay! thank you very much :)



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