A sandbag ballast is dropped from a balloon that is ascending with a velocity of 40ft/s. If the sandbag reaches the ground in 20s, how high was the balloon when the bag was dropped? Neglect air resistance.
A
5260ft
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B
6000ft
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C
5000ft
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D
5760ft
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Solution
The correct option is D5760ft Take downward as positive. Then a=g=32.8ft/s2 and v0=−40ft/s.
Using second equation of motion S=v0t+12at2=−40(20)+12(32.8)(20)2 =−800+6560=5760ft
The balloon was 5760ft above the ground.