Question

A house-top water tank is made of flat plates and is full to the brim. its height is twice that of any side. The ratio of total thrust force on the bottom of the tank to that on any side will be : 

(a) 4 

(b) 2 

(c) 1 

(d) 0.5

Answer 1

(c) 1 

The thrust on wall,

F_x = \(\rho\)g\(\bar h\)A

= \(\rho\)g \(\cfrac{2x}2\) x 2x - x

= 2\(\rho\)gx³ ...(i)

Bottom force

F_y = \(\rho\)g\(\bar h\)A  = \(\rho\)g 2x \(\times\) x \(\times\)x

= 2\(\rho\) gx³ ...(ii)

F_x /F_y = 2\(\rho\) gx³ / 2\(\rho\)gx³ = 1