A metal sheet 4 m on a side and of negligible thickness is attached to a balance and inserted into container fluid. The balance to which metal sheet is attached reads 0 . 50 N and the contact angle is found to be zero. A small amount of oil is then spread over the metal sheet. The contact angle now becomes 180 ° and the balance now reads 0 . 49 N . The surface tension of the fluid is

Question

A metal sheet 4 m on a side and of negligible thickness is attached to a balance and inserted into container fluid. The balance to which metal sheet is attached reads 0 . 50 N and the contact angle is found to be zero. A small amount of oil is then spread over the metal sheet. The contact angle now becomes 180 ° and the balance now reads 0 . 49 N . The surface tension of the fluid is, 6 . 25 × 10 - 3 N m - 1, 1 . 25 × 10 - 1 N m - 1, 4 . 25 × 10 - 2 N m - 1, 0 . 1 N m - 1

MARKS App · Accepted Answer

In the first case, when the contact angle is zero, the liquid will apply a force on the metal sheet in the downwards direction. Net force equation can be written as 0 . 50 = m g + T 4 × 2 . . . . 1 When the oil is applied on the metal sheet, the contact angle becomes 180 ° and in this case the force due to surface tension is in upwards direction. Net force equation can be written as 0 . 49 = m g - T 4 × 2 . . . . 2 From 1 - 2 , we get 16 T = 0 . 01 ⇒ T = 6 . 25 × 10 - 3 N / m

Search any question & find its solution

Looking for more such questions to practice?