Problema Solution
A ball is thrown directly up in the air from a height of 5 feet with an initial velocity of 60 ft/s. Ignoring air resistance, how long until the ball hits the ground? Use the formula 2003-19-06-00-00_files/i0080000.jpg, where h is the height of the ball in feet and t is the time in seconds since it is thrown. Round your answer to the nearest tenth. a-2.1 seconds, b-3.8. c-2.4, d-1.8
Answer provided by our tutors
If an object is thrown vertically upward with an initial velocity of v, from an original position of s, the height h at any time t is given by:
h=-16t^2+vt+s,
where h and s are in ft, t is in seconds and v is in ft/sec.
In our problem we have:
s = 5 ft
v = 60 ft/s
t = ?
h(t) = -16*t^2 + 60t + 5
The ball hits the ground when h=0 for some t<>0 that is:
-16*t^2 + 60t + 5 = 0
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t = 3.8 s
The ball hits the ground in 3.8 seconds.