John is chucking pebbles gently up to Juliet's window, and he wants the pebbles to hit the window?

Question

with only a horizontal component of velocity. He is standing 4.5 m below her window and 5.0 m from the base of the house. How fast are the pebbles going when they hit the window???

Answer 1

OK, OK, I'll bite...they are of course going zero velocity the moment they hit the window (if they do not break the glass). This follows because any horizontal velocity towards the glass would break the window. Any horizontal velocity away from the pane would not reach the glass.

Other than that, that rock could hit poor Julie's glass pane at any velocity above the minimum zero, up to and including the speed of light. If (John?) shot those rocks out of a shotgun, he could do some serious damage. Julie would not be pleased. (By the way, where's Romeo when all this is happening?)

Answer 2

now let stone be shot at angle y . vertical component of velocity v = v siny and horizontal v cosy , so v siny should become zero after 4.5 meters
V^2 =u^2-2gs (in formula capital V but the velocity with which he shot is small case v)
0 = (vsiny)^2 -20*4.5
vsiny = 3
Also time will be V=u-gt
so vsiny=10t
t=0.3 seconds
distance travelled horizontally in 0.3 seconds should be 5 mts
s=ut -1/2gt^2
5= vcosy*0.3 -5*0.09
15= vcosy
and we had 3=vsiny
dividing tany =0.2 this gives the angle at which he should shoot.
and squaring and adding v^2 = 225+9
v= (234)^1/2 is the velocity with which he should shoot.
if this is the answer give me 10.

Answer 3

Tell John not to bother throwing stones by hand. Tell him to get a high-powered BB gun. That would get Juliet's attention!