1 answer
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a. Balll #1: V = Vo + g*Tr = 0 @ max Ht.
Tr = -Vo/g = -25/-9.8 = 2.55 s. = Rise
time.
Tf = Tr = 2.55 s. = Fall time.
Tr+Tf = 2.55 + 2.55 = 5.10 s. = Time to
hit gnd.
Ball #2: h = 0.5g*t^2 = 20.0 m.
4.9*t^2 = 20
t^2 = 4.08
Tf = 2.02 s. = Fall time = time to hit gnd.
b. Ball #1: h = Vo*Tr + 0.5g*Tr^2 =
25*2.55 - 4.9*2.55^2 = 31.9 m. Above gnd.
Ball #2: Does not rise.
c. Ball #1: KE = PE = 0.5m*V^2 =
0.5*.05*25^2 = 15.625 J.
Ball #2: PE = KE = m*g*h = 0.05*9.8*20 =
9.8 J.
d. d1 + d2 = 20 m.
(25t-4.9t^2) + (4.9t^2) = 20
The squared terms cancel:
25t = 20
t = 0.8 s. = Time at which they pass each other.
h = 25t - 4.9t^2 = 25*0.8 - 4.9*0.8^2 =
16.9 m. = Ht. at which they pass each other.