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Exercise 2.36 Two sticks and a wall

Two sticks are connected, with hinges, to each other and to a wall. The bottom stick is horizontal and has length \(L\), and the sticks make an angle of \(\theta\) with each other, as shown in Figure above. If both sticks have the same mass per unit length, \(\rho\), find the horizontal and vertical components of the force that the wall exerts on the top hinge.

Also show that the magnitude goes to infinity for both \(\theta\)→ \(0\) and \(\theta\)→\(\frac{\pi}{2}\)

Note by Beakal Tiliksew
3 years, 4 months ago

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In the above figure, I have marked all the forces that are present in the system. Let the masses of the two rods be \(\displaystyle m_1\) and \(\displaystyle m_2\).

Thus,
\[m_1 = \rho L\sec\theta\] \[m_2 = \rho L\]

Considering the torque about the point A,
\[h_1(L\tan\theta) = (m_1+m_2)g\frac{L}{2}\]

\[h_1(L\tan\theta) = \rho L (1+\sec\theta)g\frac{L}{2}\]

\[\boxed{h_1 = \rho\frac{1+\sec\theta}{\tan\theta}\frac{gL}{2}}\]

Ill do the vertical force later..Ill post it as a comment

Anish Puthuraya - 3 years, 4 months ago

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Why are there no forces at the hinge joining the 2 sticks ??

Ch Nikhil - 2 years, 2 months ago

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There are forces at the hinge joining the sticks, but they are internal forces. So, they cancel each other off..

Anish Puthuraya - 2 years, 2 months ago

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@Anish Puthuraya Got it ! Thanks a lot !!

Ch Nikhil - 2 years, 2 months ago

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Nice explanation

Mardokay Mosazghi - 3 years, 4 months ago

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do you know any good book with exersises in rotational dynamics ;

Aris Nikolaidis - 2 years, 9 months ago

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Try IE Irodov or Krotov

Pranjal Jain - 2 years, 9 months ago

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