Question

In Fig, the area of cross–section of wider tube is 800 cm² . A mass of 12 kg is placed on a massless; frictionless platform as shown. h is the difference of height of water in the two limbs. h is (g = 10 ms^-2)

(1) 10 cm

(2) 6 cm

(3) 15 cm

(4) 2 cm

Answer 1

(3) 15 cm

P = The pressure on liquid due to weight placed

From Pascal’s law pressure is transmitted equally in all directions in a liquid. Therefore

P = hpg = h x 10³ x 10 Pa .....(2)

From Eqns. (1) and (2) we have

h x 10⁴ = 15 x 10²

or h = 15 x 10^-2 m = 15 cm