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Elevator Lab: Above Average Elevator Company

Last updated almost 5 years ago
21 questions
Note from the author:
Students use the concepts of Newton's 2nd Law and apparent weight to determine the acceleration and cruising velocity of an elevator.
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Before we Begin

You will be asked to show your work several times in this lab. Typing or "drawing" with your mouse/trackpad is time consuming and not easy to read, so let's try uploading a photo instead.
(1) Draw a star on a piece of paper.
(2) Open Photobooth on your computer.
(3) Take a picture of the star. Leave Photobooth open and click Show Your Work below.
(4) Click the image icon (looks like a photo of mountains) at left in the Show Your Work window. Then click My Computer.

From here you have two options:
Option A: Drag the image you wish to upload from Photobooth to the file upload window that opens in the browser. This will automatically "find" the image. Click Open, then click Add Image.

Option B: On the left of the file upload window, click Photos and then Photobooth. Find the image you wish to upload. Click Open, then click Add Image.

If needed, click the Frame tool (under the text tool) in the toolbar at right to rotate, resize or delete.

Ok! Let's get started.

You are an engineer for the Above Average Elevator Company, AAEC. AAEC is in trouble – people keep getting nauseous on your elevators! AAEC maintains the elevators at the King of Prussia mall, and you’ve sent a technician to check the acceleration of the elevator near the food court in the Plaza. You know if the acceleration of the elevator exceeds 0.9 m/s2, then people will start getting sick.

The technician brings a sophisticated scale that records the force the elevator floor exerts on him during his ride.
He gets in on the second floor and rides the elevator down to the first floor.
Watch this video of the technician's journey. (The video should start at about 32 seconds in.)
Part I: The Forces and Free Body Diagrams
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Before the elevator starts to move, is the technician's acceleration upward, downward, or zero?

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Why is this?

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When the elevator is moving downward with an increasing speed, is the technician's acceleration upward, downward, or zero?

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Why is this?

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How is this possible?

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When the elevator is moving downward at a constant speed, is the technician's acceleration upward, downward, or zero?

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Why is this?

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When the elevator is moving downward with a decreasing speed, is the technician's acceleration upward, downward, or zero?

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Why is this?

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Click "Show your Work" and draw free body diagrams for the technician in each situation:

A) before the elevator begins to move
B) while the elevator is moving downward with an increasing speed
C) while the elevator is moving downward at a constant speed
D) while the elevator is moving downward with a decreasing speed

Hint: draw all the weight vectors first. Include labels on your vectors. Be thoughtful with the relative length of the arrows you draw!

Part II: The Graph

The technician uses the scale and his computer to create a graph of his “apparent weight” (which is equal to the force of the scale on the technician, aka the normal force) during the trip. Here is a copy of the graph.
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On the graph below, clearly label the different parts of the technician’s motion, each with the letter and in a different color:

(A) before the elevator begins to move
(B) while the elevator is moving downward with an increasing speed
(C) while the elevator is moving downward at a constant speed
(D) while the elevator is moving downward with a decreasing speed
(E) after the elevator comes to a complete stop

(ignore the crazy jiggle at the end - that's when the doors open!)

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From the graph, determine the weight of the technician in Newtons.

Fg = Fearth on technician =

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How did you determine this value?

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Use the weight of the technician to calculate his mass in kilograms.
Show your work. You can draw it, type it or upload a photo.

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Use the free body diagrams you drew and information you can get from the graph to calculate the average acceleration of the elevator while it is speeding up.
Clearly show your work. You can draw it, type it or upload a photo.

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Use the free body diagrams you drew and information you can get from the graph to calculate the average acceleration of the elevator while it is slowing down.
Clearly show your work. You can draw it, type it or upload a photo.

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If the acceleration of the elevator exceeds 0.9 m/s2, then people will start getting sick. Will AAEC have to replace this elevator?

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Use the graph to estimate the amount of time it takes the elevator to speed up. Explain how you determined this value.

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Your last objective is to calculate the cruising velocity of the elevator when it is moving downward at a constant speed. Considering what you have already determined, which will be the best equation for this task?

1

Calculate the cruising velocity of the elevator when it is moving downward at a constant speed.
Clearly show your work. You can draw it, type it or upload a photo.