Question

Five uniform circular plates, each of diameter D and mass m are laid out in a pattern shown. Using the origin shown, find the y coordinate of the centre of mass of the fiveplate system.

• A. 2D/5
• B. 4D/5
• C. D/3
• D. D/5

Answer 1

The correct option is B 4D/5

$y_{cm}=\frac{\sum m_i{y}_i}{\sum m_i}$$=\frac{m\times 0+m\times D+m\times 2D+m\times D+m\times 0}{m+m+m+m+m}$$=\frac{4D}{5}$