Romeo is throwing pebbles gently up to Juliet\'s window, and he wants the pebble

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 = 7.5 m from the base of the wall

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

Express your answer to two significant figures and include the appropriate units.

2.A swimmer is capable of swimming 0.64 m/s in still water.

At what upstream angle must the swimmer aim, if she is to arrive at a point directly across the stream of a 40-m-wide river whose current is 0.50 m/s?

b)

How long will it take her?

Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

1. in vertical , at windowm, vy = 0

vf^2 - vi^2 =2 a d (in vertical)

0^2 - (v0y)^2 = 2(-9.8)(9.2 - 0)

v0y = 13.43 m/s

time taken by pebble to reach the window is t

then vf = vi + a t (in vertical)

0 = 13.43 - 9.8 t

t = 1.37 sec

in horizontal, d = (v0x) t

7.5 = (v0x)(1.37)

v0x = 5.5 m/s

when it hit, it has only horizontal component.

so v = 5.5 m/s

2. (A) 0.64 cos(theta) = 0.50

theta = 38.6 deg

(b) t = (40)/(0.64 sin38.6) = 100 sec

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