How long does a ball take to reach the ground 7 m below, if it is thrown straight up with an initial speed of 2.00 m/s?

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Answer 1 · 2014-10-29T07:49:08

u=2m/s

a= -g = -10m/#s^2#

S= -7m

t= ?

#S= ut + 1/2 at^2#
#-7= 2t + 1/2 (-10) t^2#
# 2t - 5t^2 +7 =0#
# 5t^2 -2t - 7 =0#
#t = 7/5 , -1#

As t can't be negative, t = 7/5 s = 1.4s.

Therefore, t = 1.4s