Posted by ten on Thursday, November 24, 2011 at 8:27am.
a football is kicked with a speed of 15m/s
at an angle of 35 degree from the ground.
a. how high is the ball from the ground at t=0.400s?
b. how fast is it moving(s) after being kicked?
c. at what tvalues is the ball 2m from the ground?

science  Henry, Friday, November 25, 2011 at 7:52pm
Vo = 15m/s @ 35deg.
Xo = hor. = 15cos35 = 12.29m/s.
Yo = ver. = 15sin35 = 8.60m/s.
a. h = Yo*t + 0.5g*t^2,
h = 8.60*0.4  4.9*(0.4)^3 = 2.66m.
b. Vo = 15m/s.
c. d = Yo*t  4.9*t^2 = 2m,
8.60t  4.9t^2 = 2,
4.9t^2 + 8.6t  2 = 0.
Tr = o.27594s. = Time to rise to 2m above ground. Use Quadratic Formula and choose shortest time.
hmax = (Yf^2  Yo^2) / 2g,
hmax=(0  (8.60)^2) / 19.6 = 3.77m.
d = Yo*t + 4.9t^2 = 3.77  2 = 1.77m.
0 + 4.9t^2 = 1.77,
t^2 = 0.361,
Tf = 0.60s = Time to fall to 2m. above ground.
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