SOLUTION: During the construction of a high-rise building, a worker accidentally dropped his portable electric screwdriver from a height of 400 ft. After t sec, the screwdriver had fallen a
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Question 1153146: During the construction of a high-rise building, a worker accidentally dropped his portable electric screwdriver from a height of 400 ft. After t sec, the screwdriver had fallen a distance of
s = 16t2 ft.
(a)
How long did it take the screwdriver to reach the ground?
(b)
What was the average velocity of the screwdriver between the time it was dropped and the time it hit the ground?
What was the velocity of the screwdriver at the time it hit the ground?
(a) To determine "how long . . . ", solve the equation
16*t^2 = 400.
It is easy to do
t^2 =
t^2 = 25
t = sqrt(25) = 5 seconds. ANSWER
(b) The average velocity = = = 80 ft/s. ANSWER
(c) In Calculus, velocity is first derivative of the distance over the time
v = = = 2*16*5 = 160 ft/s.
In Physics, v = g*t, where g is the gravity acceleration g = 2*16 ft/s^2 = 32 ft/s^2, t = 5 seconds,
so v = 32*5 = 160 ft/s, giving the same ANSWER
