An object is thrown vertically from a height of #9 m# at # 24 m/s#. How long will it take for the object to hit the ground?

1 Answer
Jun 2, 2016

Answer:

I found: #5.2s#

Explanation:

I would suppose that the velocity is in the upwards direction because it is positive and so in:

#y_f-y_i=v_it+1/2at^2#
with:
#y_f=0# the ground
#a=g# downwards.

we have:

#0-9=24t-1/2*9.8t^2#
#4.9t^2-24t-9=0#

Using the Quadratic Formula:
#t_(1,2)=(24+-sqrt(576+176.4))/9.8=#
#t_(1,2)=(24+-27.4)/9.8=#
#t_1=5.2s#
#t_2=-0.3s#