Properties Of Solids And Liquids Question 382
Question: A thin metal disc of radius r floats on water surface and bends the surface downwards along the perimeter making an angle q with vertical edge of the disc. If the disc displaces a weight of water W and surface tension of water is T, then the weight of metal disc is[AMU (Med.) 1999]
Options:
A) $ 2\pi rT+W $
B) $ 2\pi rT\cos \theta -W $
C) $ r\pi r\theta +W $
D) $ W-2\pi rT\cos \theta $
Show Answer
Answer:
Correct Answer: C
Solution:
Weight of metal disc = total upward force = upthrust force + force due to surface tension = weight of displaced water $ +Tcos\theta (2\pi r) $
$ =W+2\pi rTcos\theta $
