A boy throws a stone horizontally from the top of a cliff of height h toward the
ID: 2165238 • Letter: A
Question
A boy throws a stone horizontally from the top of a cliff of height h toward the ocean below. The stone strikes the ocean at distance d from the base of the cliff. In terms of h, d, and g, find expressions for the following.(a) the time t at which the stone lands in the ocean
t =
(b) the initial speed of the stone
vxi =
(c) the speed of the stone immediately before it reaches the ocean
vf =
(d) the direction of the stone's velocity immediately before it reaches the ocean
?f = below the horizontal
Explanation / Answer
up = +direction
a) vertical displacement = -h = (-g)t2/2
t = (2h/g)
b) initial speed vxi = d/t = d[g/(2h)]
c) vertical final speed vy = (2gh)
v = (vxi2 + vy2) = [d2g/(2h) + 2gh]
d) tan-1(vy/vxi) = tan-1(2h/d)
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