Question

A child swinging on a swing in sitting position, when she stands up then the time period of the swing will

• A. Increase
• B. Decrease
• C. Remains same
• D. Increases of the child is long and decreases if the child is short

Answer 1

The correct option is B Decrease

$T=2\pi \sqrt{l_{eff}/g};l_{eff}$ decreases when the child stands up.

$T=2\pi \sqrt{\frac{L}{g}}$

If $L$ is the distance between the centre of mass of the mass to the point of suspension, when the boy stands, his centre of mass is raised and L will decrease. Therefore, the time will decrease.