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A 1.6 kg brick is dropped from the top of a 60 m tower. As the brick falls, it experiences an average drag force of 2 N over the first 2 seconds of flight. How far above the ground will the brick be after these first 2 seconds?
Title
A 1.6 kg brick is dropped from the top
Your Result
Correct
Difficulty
Hard
Your Pace
0:01
Others' Pace
2:26
Text Explanation
17.1 m: This answer choice is incorrect, because the brick will be more than 17.1 meters above the ground after 2 seconds.
42.9 m: This answer choice is correct. If there were no drag forces, the force on the brick would be (10 m/s2)ยท(1.6 kg) = 16 N.
According to the question, the average drag force is 2 N, so that makes the net force on the object 14 N. You must then use Newton's second law to find the acceleration:
14 = 1.6a
a = 9
Knowing the acceleration, you can plug it into the kinematics formula x = (1/2)at2 + vot + xo.
x = (1/2)(9)(22) = 18 m
Since the brick started at 60 m, it will be at 60 - 18 = 42 meters after 2 seconds. The only answer that is close is this one.
35.9 m: This answer choice is incorrect, because the brick will be more than 35.9 meters above the ground after 2 seconds.
24.1 m: This answer choice is incorrect, because the brick will be more than 24.1 meters above the ground after 2 seconds.
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