Calculating Gravity from Inclined plane

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The discussion revolves around calculating gravitational acceleration (g) using data from a ball rolling down an inclined plane. The user initially calculated acceleration (a) from time and distance data but found their g value significantly lower than expected. They explored the effects of the ball's rolling motion and attempted to incorporate the moment of inertia using the parallel axis theorem, but struggled with the algebraic relationships involved. The conversation highlighted the complexities of relating linear and rotational motion, particularly in a non-flat scenario, with participants providing guidance on deriving the necessary equations. Ultimately, the user expressed frustration over the advanced nature of the problem and the lack of clarity in available resources.
  • #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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