Atwood's Machine with Spring Scale Part 2: Qualitative Testing Experiment

Aim

Aim here

Prior Knowledge

• Types of motion.
• Qualitative version of Newton's second law: the change in the motion of an object always occurs in the direction of the unbalanced force exerted on the object.
• Understanding of what a scale reads.

Description of the Experiment

Notice the reading on the scale when Luis is holding the apparatus steady. Use your knowledge of the relationship between the unbalanced force and changes in motion (relationship between the force diagram and the motion diagram) to predict what will happen to the reading of the scale when Luis removes his hand.

Addtional Information

The left-hand object has a mass of 200g, the right-hand objects have a combined mass of 300g.

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Questions

• Draw a motion diagram for the object on the left (orange and blue together) after Luis lets the spring scale go.
• Draw a free-body diagram for the object on the left (orange and blue together) before and right after Luis lets the spring scale go. Is the second free body diagram is consistent with the motion diagram? Should it be? Explain.
• Which of the forces on your free body diagram are related to the reading of the scale? In other words, what does the scale read?
• Use the answers to the previous questions to predict what will happen to the reading of the scale when Luis lets it go.
• Observe the experiment and decide whether your prediction was confirmed.
• What was the principe on the basis of which you made the prediction? What can you say about the validity of this principle based on the outcome of the experiment?
• What is the difference between the principle and the prediction?