How fast are the pebbles going when they hit her window.?

Romeo is chucking pebbles gently up to Juliet's Window, and he wants the pebble to hit the window with only a horizontal component of velocity. He is standing at the edge of a rose garden 4.5 m below her window and 5.0 m from the base of the wall. How fast are the pebbles going when they hit her window?

How fast are the pebbles going when they hit her window.?
The pebble would reach 5 m height with 0 vertical velocity if starting velocity was Vi = g*t where t is flight time, i.e. h = Vi*t - g*t^2/2 = g*t^2 - g*t^2/2 = g*t^2/2, or t = sqrt(2h/g).


Then horizontal velocity should be Vx = d/t = d/sqrt(2h/g)


d = 5, h = 4.5, g = 9.8
Reply:When you know time of ascent, you will know how fast


they hit the window.


First you need time of ascent.


from S= .5gt^2 get t=Sqrt(2s/g)=sqrt(9/10)=.95 sec.


Horizontal velocity is 5m/.95 sec =5.3m/s