Spring scale up and down: Qualitative Testing Experiment

Aim

Test the idea that the object changes its motion in the direction of the unbalanced force (sum of all forces) exerted on the object.

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 (sum of forces) exerted on the object.
• Understanding of what a scale reads.

Description of the Experiment

David (1)abruptly lifts the spring with an object attached ot it and then (2) abruptly stops the scale. Predict the changes in the reading of the scale in experiments (1) and (2) compared to the reading when the scale and the object are stationary. To make the prediction use motion diagrams and force (free-body) diagrams.

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Questions

• Draw a motion diagram for the object attached to the scale when the scale is stationary, then being pulled up and then stops.
• Draw a free-body diagram for the object attached to the scale when the scale is stationary, then being pulled up and then stops. Decide whether the free-body diagram is consistent with the motion diagram. How is the free-body diagram related ot the reading of the scale?
• Use the free-body diagram and the idea under test to make a prediction of the relative readings of the scale.
• Observe the experiment and reconcile the outcome with your prediction.