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If an object is thrown vertically upward, the height (h) at any time (t) is given by: h...

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kristenmarieb... | Student, Grade 10 | (Level 1) Valedictorian

Posted May 25, 2013 at 2:46 AM via web

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If an object is thrown vertically upward, the height (h) at any time (t) is given by: h = 16t^2+vt

A package is thrown downward w/initial velocity of -5 ft/sec. from a helicopter at 300 ft. What is the height of the package in 2 sec and how long does it take to hit the ground.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted May 25, 2013 at 3:01 AM (Answer #1)

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When an object is thrown vertically upward, the height at any time t is given by the expression h = 16*t^2 + v*t.

If a package is thrown downward from a helicopter at 300 ft with an initial velocity 5 ft/s, the height of the package after 2 seconds is:

300 - (16*2^2 + 5*2) = 300 - 74 = 226 ft.

The time taken by the package to hit the ground is the solution of 300 - (16*t^2 + 5*t) = 0

=> 16t^2 + 5t - 300 = 0

The positive solution of this equation is `(5*sqrt(769)-5)/32` s

The height of the package in 2 seconds is 226 ft and it takes `(5*sqrt(769)-5)/32` s to strike the ground.

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