MCQ
A flat horizontal board moves up and down in $SHM$ of amplitude $\alpha$. Then the shortest permissible time period of the vibration such that an object placed on the board may not lose contact with the board is
- A$2\pi \sqrt {\frac{g}{\alpha }} $
- ✓$2\pi \sqrt {\frac{\alpha}{g }} $
- C$2\pi \sqrt {g \times \alpha } $
- D$\frac{1}{{2\pi }}\sqrt {\frac{g}{\alpha }} $


