A boy throws a ball off the top of a 30m high building with a speed of 10m/s at an angle of 30 degrees to the horizontal. How far from the base of the building does the ball strike?

Question

A boy throws a ball off the top of a 30m high building with a speed of 10m/s at an angle of 30 degrees to the horizontal.  How far from the base of the building does the ball strike?

I broke in up into 2 dimensional:
X horizontal values: Xi=0 Xf=? Vi=8.6m/s. Vf=? a=0
Y vertical values: Xi=0, Xf=15m, Vi=5, Vf? a=9.82.  I then solved for time in the Y then used the distant formula to find my answer. 11.3 m away.  Is this right?

bobpursley · Accepted Answer

vertical: hf=hi+vi*t-gt^2 /3 0=30+10sin30*t-4.9t^2 time 4.9t^2-5t-30=0 I get about 3 sec horizontal: distance=10cos30 * 3.03 sec which is not your answer.