# The differential height of the manometer and the force needed to hold the container in place are to be determined

A cylindrical container equipped with a manometer is inverted and pressed into water. The differential height of the manometer and the force needed to hold the container in place are to be determined

Since pression in $$A$$ is the same as pression in $$B$$ i got

But since i cant find the value of $$d$$ i am unable to solve the rest of the exercice. Any suggestions?

• What d? You have D given. But why would you need that? H is related to the pressure by the SG. Sep 26, 2021 at 14:20
• because the pression in A is p(atm)+ρ(SG)*gh + ρ(air)*gd and i know that p(atm)=0 but dont know the value of d Sep 26, 2021 at 14:27
• Well since you have just been handed the answer, you won’t learn much since you didn’t work for it. Sep 26, 2021 at 15:02
• but why i dont need the value of d? Sep 26, 2021 at 15:14
• Where is d on your diagram? Sep 26, 2021 at 15:16

Assume the tank is weightless, then

$$F = 20\gamma_w A$$

$$20\gamma_w = \gamma_{mf}h$$,

$$SG = \dfrac{\gamma_{mf}}{\gamma_w} = 2.1$$

Note the tank is pressurized internally by the floating bottom lid "A".

the force need to hold the cylinder down is

$$F=\pi \frac{25^2}{4} 20/1000cm*1.033kg/atm- \text{weight of the cylinder}$$

the difference between the two sides of the manometer is

$$h=20cm/2.1=9.523cm$$

# Edit

responding to OP's comment on how to measure the effective weight of partially submerged cylinder after deducting buoyancy.

$$W_{submerged cylinder}= W_{dry} - \pi *25*20*t$$

• where t is the thicknesses of the cylinder. and weight is in grams.
• how you got those expressions ? Sep 26, 2021 at 15:25
• the pressure of the water at depth d = d*\Rho*g Sep 26, 2021 at 16:32
• and how do you calculate the weight of the cylinder since its partially immerse? (i know its not 6*9.81) Sep 26, 2021 at 19:04
• the weight of cylinder is dry weight - 25pi* thickness* 20 grams. Sep 26, 2021 at 19:31
• and how is that equal to 65N (which is the value I should have) ? if i do what you said i got 1570N Sep 27, 2021 at 11:55