A golf ball is hit at 42.0 m/s at an angle of 20° with the ground. How far away does it land?
Vertical problem
Vi = 42 sin 20 = initial speed UP
calculate that, we need it.
How long until it comes down?
height equation: h = Hi+Vit-4.9t^2
0 = 0 + Vi t - 4.9 t^2
so
Vi t - 4.9 t^2 = 0
t (Vi-4.9t) = 0
we all know we are at the ground at t = 0
but
now we know that it is back at the ground at t = Vi/4.9
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So now we can do the horizontal problem
u = 42 cos 20 = horizontal speed forever
and finally
d = u t
The End