Mapd Map Physics saplingl leaming Suppose water is raised by capillary action to

Question

Mapd Map Physics saplingl leaming Suppose water is raised by capillary action to a height of 6.45 cm in a glass tube. Refer to the angle values given in the table below to answer the following questions. Enter a positive number for height if the water is raised above the surrounding water level, and a negative number if it is pushed below What height will water reach in a paraffin tube of the same radius?Interface Ctact Angle 0° 107 90° water/glass Number em What height will water reach in a silver tube of the same radius? cm

Explanation / Answer

The height h of a liquid column is given by:

           h = 2 cos / g r,

where

is the liquid-air surface tension,

is the contact angle,

is the density of liquid,

g is local acceleration due to gravity and

r is radius of tube (length).

H glass = 2 cos / g r

= 2 cos 00 / g r

= 2 / g r         (since cos 00 = 1)

= 6.45 cm           (given)

Therefore 2 / g r = 6.45 cm                  - (1)

h paraffin = 2 cos / g r

= 6.45 cos        (using equation 1)

= 6.45 x cos 1070

= 6.45 x 0.29

= 1.89 cm

h silver = 2 cos / g r

= 2 cos 900 / g r

= 2 0 / g r      (since cos 900 = 0)

= 0 cm

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