Calculating Gravity from Inclined plane

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Homework Help Overview

The discussion revolves around calculating the acceleration due to gravity (g) using an inclined plane setup with a rolling ball. The inclined plane is 2 meters long with a height of 6.1 cm, and participants are provided with distances and corresponding times for the ball's descent.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss plotting data to find acceleration and explore the effects of a rolling ball on the calculation of g. Some express uncertainty about the correct formulas to use, particularly regarding the moment of inertia and the relationship between linear and angular velocity.

Discussion Status

The discussion is ongoing, with various participants sharing their calculations and questioning the assumptions behind their approaches. Some have provided partial calculations and are seeking clarification on the effects of the ball's rolling motion, while others express frustration with the complexity of the problem.

Contextual Notes

Participants note the absence of certain key information, such as the mass of the ball, which complicates their calculations. There is also mention of homework constraints that may limit the depth of exploration.

  • #31
Fat_Squirrel said:
Which means our ratio should be 1 / (2/5 r^2/x^2 + 1) ??
Almost.
I'm afraid I may have confused you a little.
When dealing with bodies that are both rotating and moving linearly, there are two main ways of thinking of it:
- as a linear movement of the mass centre, plus a rotation about the mass centre, or
- as a rotation about the instantaneous centre of rotation.
With the first approach, the total KE is ##\frac 12 m(v^2+\frac 25 r^2\omega^2) = \frac m2 (x^2+\frac 25 r^2)\omega^2##, exactly the result the second approach gives.
Hence the fraction of the total KE that is linear is ##\frac{x^2}{x^2+\frac 25 r^2}##.
Can you see how to get from there to an expression for v as a function of the height loss?
 
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  • #32
1/[x^2 / (x^2 + 2/5 r^2)] * a * sinθ

so 1/[10.41^2 / (10.41^2 + 2/5 * 15^2) * 0.1646 * (0.061/2)] = 9.866

Answer looks good,how'd I go with this one?
 
  • #33
Fat_Squirrel said:
1/[x^2 / (x^2 + 2/5 r^2)] * a * sinθ

so 1/[10.41^2 / (10.41^2 + 2/5 * 15^2) * 0.1646 * (0.061/2)] = 9.866

Answer looks good,how'd I go with this one?
Yes, I believe that works.
 
  • #34
haruspex said:
Yes, I believe that works.

Once again, thanks for your help and patience. Will let you know if we got the answer my teacher expected.
 
  • #35
haruspex said:
Yes, I believe that works.

here's the solution they provided - https://youtu.be/IED3ujslfPY. I got a slightly different answer because I calculated acceleration differently.
I used values associated with t^2 and ran least squares on them to get my value for the slope, he used √d values - i thought they'd give same answer, but slightly different it seems.

Anyway if I use his value for acceleration I get the exact same answer he does. Thankfully my answer was within the margin of error. Thanks again.
 

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