# physics

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1.A stone fired straight upwards from the top a 50m high bridge fall into water below it 12seconds later.what was its initial velocity? how high above the bridge did it go?

• physics -

0 = 50 + Vi t - 4.9 t^2
0 = 50 + Vi (12) - 4.9 (144)
12 Vi = 705.6 - 50 = 655.6
Vi = 54.6 m/s

0 = 54.6 - 9.8 t
t = 5.57 seconds rising
h above bridge = 0 + Vi t - 4.9 t^2
= 54.6(5.57) - 4.9 (5.57)^2
= 152 m

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