A ball is thrown horizontally from the roof of a building 45m tall and lands 24m from the base. What is the ball's initial speed?

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Answer 1 · 2017-10-03T06:34:25

#8m^(-1)#

we have

using the usual x-y axes

initial vertical velocity
#" "u_y=0ms^(-1)#

initial horizontal velocity
#" "u_x" "ms^(-1)#

vertical displacement
#" "s_y= -45m#

horizontal displacement
#" "s_x=24m#

acceleration due to gravity

#g=-10ms^(-2)#

consider vertical components

#s_y=u_yt+1/2at^2#

#=>-45=0-1/2xx10t^2#

#=>t^2=90/10=9#

#:.t=3s#

horizontally there is no acceleration so

#u_x=s_x/t#

#u_x=24/3=8ms^(-1)#