1. Mercury makes an angle of 130- with respect to the vertical when in contact with clean glass. How far will mercury depress in a clean, 10-mm-diameter glass tube if sHg ¼ 0.467 N=m.
2. A steel needle of length L and radius r will ?oat in water if carefully placed. Write an equation that relates the various variables for a ?oating needle assuming a vertical surface tension force.