A thread of mercury of 10.2 g is in a tube of uniform cross section 0.1cm 3 . Calculate the length of thread. The density of mercury is 13.6g/cm 3
we know that
density = mass / volume
or
d = m / V
here
d = 13.6 gm/cm3
m = 10 gm
and V = πr2.l = A.l
where A is the area of cross-section = 0.1 cm2 and l is the length
thus, we have
13.6 = 10 / (A.l)
or
l = 10 / (13.6 x A) = 10 / (13.6 x 0.1)
or
l = 10 / 1.36
thus, the length of the tube will be
l = 7.352 cm