Question

Romeo is throwing pebbles gently up to Juliet's window, and he wants the pebbles to hit the window with only a horizontal component of velocity. He is standing at the edge of a rose garden h = 9.2 m below her window and L = 9.4 m from the base of the wall (Figure 1). How fast are the pebbles going when they hit her window? Express your answer to two significant figures and include the appropriate units.

Answer 1

final vy = 0 = vy - 9.81 t

vy = 9.81 t
final y = 9.2m = vyt - g/2 t^2= vy t - 4.905 t^2

9.20 m = 9.81t* t - 4.905 t^2 = 4.905 t^2
t = sqrt(9.20m/4.905m/s^2) = 1.369 s
final vx = original vx =vx
final x = 9.4 m = vx t
at window
vx = 9.4m /t =9.4/1.369 = 6.866 m/s ..................ans
vy = 0

so, the pebble is going to hit with 6.866 m/s speed