Posted by Emily on Monday, July 15, 2013 at 9:46pm.
When a ball is thrown in the air at 15mps from a height of 1 ft, how long does it take for the ball to hit the ground?

Math  mahesh, Tuesday, July 16, 2013 at 1:14am
v=ugt or 0=159.81t since final velocity is 0 and ball is going against gravity. Thus t=1.53 sec.
s=ut.5gt^2=15.5x9.81x(1.53)^2
s=22.9511.48=121.47 which is the height the ball will go. From there it falls freely for a height of 11.47+1=12.47 ft.
s=0xt+.5x9.81xt^2 or t=(12.47x2/9.81)=1.59 secs.

Math  mahesh, Tuesday, July 16, 2013 at 1:52am
PS: s=11.47 which has appeared as 121.47 at one place in 4th line.

Math  Steve, Tuesday, July 16, 2013 at 9:55am
since 1 ft = .3 m,
s(t) = .3 + 15t  4.9t^2
it hits the ground when s=0, so
.3 + 15t  4.9t^2 = 0
t = 3.08 sec
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