What Fraction of Initial Height Causes a Plank to Lose Wall Contact?

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SUMMARY

The discussion focuses on determining the fraction of the initial height at which a plank of length 2L loses contact with a wall as it slips downward without friction. Key equations include the normal forces N1 and N2 acting on the plank, and the relationship between the angle θ and the coordinates x and y of the center of mass. The plank loses contact when N1 equals zero, leading to the derived second-order differential equation d²θ/dt² + (3g/2L)cotθ(sinα-sinθ) = 0. The energy conservation approach is highlighted as an effective method to solve the problem.

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  • #31
Tanya Sharma said:
One thing I need to clarify is that θ is measured from the horizontal with clockwise being the direction of increasing θ .

Does that mean direction of increasing θ has to be considered positive ?
Yes, cw would be the positive direction for θ.

Does this reflect on the direction of torque as well with clockwise torque being considered positive and ccw negative ?
Yes. I believe you set up your torque equation with the correct signs.
 

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