Answer to Question #23642 in Mechanics | Relativity for rosko
There is a constant gravitation force
F = mg
acting on the ball during its fly.
This force is directed to the ground and is opposite tovy.
Hence the ball moves uniformly along x-axis and withconstant acceleration -g along y-axis, so vx is constant:
vx(t) = vx(0)
vy(t) = vy(0) -g*t.
Thus the ball moved t=3 seconds and fly s=50.0 m, whenceits horizontal velocity, i.e. vx(t) is equal to
vx = s/t = 50/3= 16.667 m/s
Further notice that the ball flies up the same time as itgoes down,
and at the maximal point the time was 1.5 seconds and itsvelocity vy=0, whence
vy(1.5) = vy(0)- 9.8 * 1.5 = 0
vy(0) = 9.8 *1.5 = 14.7 m/s.
Hence the full initial velocity is v = sqrt(vx(0)^2+vy(0)^2)
= 22.223 m/s
Let alpha be the angle of the kick.
tan(alpha) =vy/vx = 14.7/16.667 = 0.88198
alpha =acrtan(0.88198)= 0.72277 rad = 41.412 degree
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