What Is the Maximum Acceleration of an Empire State Building Elevator?

AI Thread Summary
The discussion revolves around calculating the maximum upward and downward acceleration of the Empire State Building's elevators based on varying scale readings. The user attempts to apply the formula Fnet = N - Fg but struggles to arrive at the correct answers. Clarifications are provided regarding the net force exerted on the scale, emphasizing that the scale measures the net downward force. The conversation highlights the importance of correctly applying Newton's second law and understanding the relationship between net force, mass, and weight. Ultimately, the user seeks assistance in resolving their calculations for accurate acceleration values.
pdonovan
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Question:
You've always wondered about the acceleration of the elevators in the 101-story-tall Empire State Building. One day, while visiting New York, you take your bathroom scale into the elevator and stand on it. The scale reads 150 lbs as the door closes. The reading varies between 120 lbs and 170 lbs as the elevator travels 101 floors.

a.)What is the maximium acceleration upward?
b.)What is the maximium magnitude of the acceleration downward?


I used the formula Fnet = N - Fg and still cannot get the correct answer.
I currently have ma = N - mg where m = 77.11kg, N = 756N, and g = 9.8.
So, 77.11a = 756 - 77.11(9.8)

Where did I go wrong?
Thank you for any help!
 
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Well, you know what the Fnet is.

If your just standing on the ground not moving, it's just your weight (well, it's zero if you count the ground pushing back up on you).

Bottom line is the scale is going to show the net downward force you exert on it. So you may want to set it up
Fnet = m*a + Fweight
 
How can Fnet = ma + Fweight when Fnet = ma?
 

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