Question

A rod of length $L$ leans against a smooth vertical wall while its other end is on a smooth floor. The end that leans against the wall moves uniformly vertically downward. Select the correct alternative

• A. The speed of lower end increases at a constant rate
• B. The speed of the lower end decreases but never becomes zero
• C. The speed of the lower end gets smaller and smaller and vanishes when the upper end touches the ground
• D. The speed of the lower end remain constant till upper end touches the ground

Answer 1

Answer: (C)

Using constraint motion relation $V \cos \theta=v \sin \theta$ $V=v \tan \theta$ As $\theta$ keeps on decreasing, tan $\theta$ will also decrease and at last $\theta$ will become zero and $V=0$,