A football is kicked at ground level with a speed of 18.0 m/s at an angle of 35.0 degrees to the horizontal. How much later does it hit the ground?

Question

anonymous · Answer

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x- direction

v = 18 cos 35
   = 14.745 m/s

y- direction

initial velocity = u = 18 sin 35
                          = 10.324m/s

a = 9.8 m/s^2
final velocity = v = 0

$$t = (v-u) \div a$$

t = (0 - 10.324) / -9.8
  = 1.05s

Since this is the time it takes to just go up, we double it to know the total time. 
Hence, 

t = 1.05 X 2 = 2.11s

It hits the ground 2.11s later.