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I can't understand how the cross product of $\hat{\mathbf{z}}$ and $\hat{\mathbf{r}}$ works in the equation of centrifugal force and the same cross product between $\hat{\mathbf{z}}$ and $\hat{\boldsymbol{\theta}}$ in the equation for Coriolis force. Please help me understand this.

According to my understanding, the cross product between $\hat{\mathbf{z}}$ and $\hat{\boldsymbol{\theta}}$ is along the direction that is completely opposite to the direction that is given here, i.e. rotate the Coriolis vector ($\mathbf{F}$) given in the answer by 180°. I can't even begin to comprehend how the direction of centrifugal force is found here.

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    $\begingroup$ You need to ask a conceptual question. Saying you don't understand is not sufficient information. $\endgroup$
    – joseph h
    Commented Jul 26, 2021 at 5:49
  • $\begingroup$ @joseph h ,according to my understanding the cross prod between z cap and θ cap is along the direction that is completely opposite to the direction that is given here ,(ie) the coriolis force is along the direction that is completely opposite to the one given here (rotate the F coriolis vector given as the answer by 180°,I can't even begin to comprehend how the direction of Centrifugal force is found here $\endgroup$
    – Harry Case
    Commented Jul 26, 2021 at 5:59
  • $\begingroup$ I have added your comment to your original question. $\endgroup$
    – joseph h
    Commented Jul 26, 2021 at 6:01
  • $\begingroup$ @joseph j thank you $\endgroup$
    – Harry Case
    Commented Jul 26, 2021 at 6:21

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This question is completely screwed up, and the answer is very wrong.

  1. Centrifugal force is given by $ {\displaystyle -m{\boldsymbol {\omega }}\times ({\boldsymbol {\omega }}\times {\boldsymbol {r}})}$. There is a minus sign missing in the solution.
  2. There are two simultaneous rotations in the problem, meaning the total centrifugal force is a vector sum of both. This can be directly visualized by noting the fact that for each circular motion the centrifugal force is radially outward and taking a vector sum of those two.
  3. The Coriolis force is given by ${\displaystyle -2m{\boldsymbol {\omega }}\times \left[\operatorname {d} {\boldsymbol {r}}/\operatorname {d} t\right]}$, directed along $-\hat{z}\times\hat{v}$, where v is the velocity vector of the particle. $-\hat{z}\times\hat{v}=\hat{r}_{small}$, where $r_{small}$ is the coordinates centered at the smaller circle.
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