Answer:
[tex]r_{cm} = 0.13 m[/tex]
Explanation:
Let the position of center of the see saw is origin
so we will have
[tex]m_1 = 40 kg[/tex]
[tex]r_1 = 0[/tex]
[tex]m_2 = 60 kg[/tex]
[tex]r_2 = -1.5 m[/tex]
[tex]m_3 = 75 kg[/tex]
[tex]r_3 = + 1.5 m[/tex]
now we will have
[tex]r_{cm} = \frac{m_1 r_1 + m_2 r_2 + m_3 r_3}{m_1 + m_ 2 + m_3}[/tex]
[tex]r_{cm} = \frac{40(0) + 60(-1.5) + 75(1.5)}{40 + 60 + 75}[/tex]
[tex]r_{cm} = 0.13 m[/tex]