What Determines Rebound Height in a Physics Lab Experiment?

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Homework Help Overview

The discussion revolves around a physics lab experiment involving the measurement of rebound heights of a ball dropped from various heights. The original poster presents a linear model derived from their experimental data, questioning the implications of the model when the drop height is zero.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the validity of the linear model used to predict rebound height, questioning the assumptions behind the model, particularly regarding its applicability at lower drop heights. Some participants analyze the mathematical implications of the model, while others inquire about the specifics of the measurement process.

Discussion Status

The discussion is active, with participants providing insights into the limitations of the model and questioning the conditions under which it holds true. There is an exploration of the relationship between drop height and rebound height, with no consensus reached yet on the best approach to address the original poster's query.

Contextual Notes

Participants note that the model may not be applicable for drop heights below a certain threshold, specifically questioning the accuracy of measurements and the definition of the height from which the ball was dropped.

ludi_srbin
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In Friday we did simple lab in Physics. We took ball and dropped it measuring dropping height and rebound height. We did 10 trials and 10 times for every trial. We started from 100 cm and went all the way to 10 cm. Then we made a model y =0.75x+2 cm. Where x is dropping height in cm and y is rebound height, also, in cm. We could use this model to predict rebound height from any height. Well the accuracy wasn't really the priority. My question is if I "drop" the ball from height of zero cm I would get reboung height 2 cm, according to my model. How can that be?
 
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Hmm, in fact, since the ball never has the rebound height that's greater than the height it was dropped from. So:
[tex]\frac{3}{4}x + 2 \leq x \Leftrightarrow \frac{1}{4}x \geq 2 \Leftrightarrow x \geq 8[/tex]
For any x < 8, it will return a false value.
So the formula can be true for x >= 8 cm. And that's why the smallest height in your work is 10cm, not 0 cm.
Viet Dao,
 
Apparantly either a linear model is no good for this situation, or your measurements were too imprecise or inaccurate.
 
Up to which point did you measure the heights of the ball? It's bottom, middle or top?
 

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