# Physics

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A sniper fires a bullet at 120 m/s at 30° above the horizontal from the roof top of a 35 m high parking garage. If the bullet strikes the level ground beside the parking garage:

a) How long was the bullet in the air?

b) How far from the base of the parking garage did the bullet land?

c) At what angle did the bullet land?

• Physics -

Vo = 120m/s[30o]
Xo = 120*cos30 = 103.9 m/s.
Yo = 120*sin30 = 60 m/s.

a. Y = Yo * g*Tr = 0
Tr=-Yo/g = -60/-9.8 = 6.12 s. = Rise time.

h = ho + (Y^2-Yo^2)/2g
h = 35 + (0-(60^2))/-19.6 = 218.7 m.
Above gnd.

h = 0.5g*t^2 = 218.7
4.9t^2 = 218.7
t^2 = 44.63
Tf = 6.68 s. = Fall time.

Tr+Tf = 6.12 + 6.68 = 12.8 s. = Time in
air.

b. d = Xo*(Tr+Tf) = 103.9m/s * 12.8s =
1330 m.

c. Y^2 = Yo^2 + 2g*h
Y^2 = 0 + 19.6*218.7 = 4286.52
Y = 65.5 m/s.

Tan A = Y/Xo = 65.5/103.9 = 0.63041
A = 32.2o

• Physics -

TYPO: Change Y = Yo*g*Tr = 0 to
Y = Yo + g*Tr = 0

• Thanks Henry -

Thanks Henry,

You're a good guy!

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