You and three other physics 9A students are in a glass elevator on your way to t
ID: 2059310 • Letter: Y
Question
You and three other physics 9A students are in a glass elevator on your way to the bar at the top of the Bank of America building in SF. The elevator is moving upward at a constant speed of 2.50m/s. A bolt in the elevator ceiling 3.00m above the elevator floor works loose and fallsa)How much time does it take for the bolt to fall tothe elevator floor?
b) What is the speed of the bolt just as it hits the elevator floor according to one of you standing in the elevator
c)What is the speed of the bolt as it hits the floor, according to a physics 7A student who just just happens to be standing outside as you pass, and sees the bolt moving through the glass doors?
d)According to a physics 7A student in part c, what distance did the bolt travel between the ceiling and the floor of the elevator
Explanation / Answer
Please ask if you have any doubt.I will help you.
The distance = s =3.00m
g = 9.80m/s2 .
speed of elevator = 2.50m/s
Thus the 3m will be covered by freely falling bolt and constantly moving lift.
Therefore ,0.5(9.8)t2 + 2.50t = 3
4.9t2 + 2.50t - 3 = 0 solving gives t = 0.57s
a) 0.57s
b) speed of bolt = V = (9.8m/s2)(0.57s) = 5.6m/s.
According to the class 7A student the bolt would have travelled 3m completely.
d) 3m
c) The speed = V = ((2)(9.8m/s2)(3m))0.5 = 7.7m/s.
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