An object is suspended from a spring scale first in air, then in water, as shown

Question

An object is suspended from a spring scale first in air, then in water, as
shown in the figure above. The spring scale reading in air is 17.8 N,
and the spring scale reading when the object is completely submerged
in water is 16.2 N. The density of water is 1000 kg/m3 .
(a) Calculate the buoyant force on the object when it is in the water.
(b) Calculate the volume of the object.
(c) Calculate the density of the object.
(d) How would the absolute pressure at the bottom of the water change
if the object was removed?
___ It would increase. ___ It would decrease ___ It would remain the same.
Justify your answer.

Explanation / Answer

hi, this is a same question with just different numericals . I am posting both question and answer. Also it may serve well and be helpful to you if you practice on your own . :) Please rate me Lifesaver !!!! An object is suspended form a spring scale first in air, then in water. the Spring scale reading in air is 5N? and the spring scale reading when submerged in water is 3N , the density of water is 1000 kg/m^3 a) caluculate the buoyant force in water b) calucualte the volume of object c) calculate the density of object d) how would the aboslute pressure at the bottom of the water change if the object was removed? explain your answer Ans: For our purposes, neglect air's buoyant force. Force balance on it in air: Tair = m*g Force balance on it in water: Tension (Tw): upward Buoyancy (B): upward Weight (m*g): downward Thus: Tw + B = m*g Solve for B: B = m*g - Tw Or, B = Tair - Tw What causes this buoyancy force? Because it is a situation of fluid statics, the buoyancy force equals weight of water displaced. B = rho_w*V*g Thus: rho_w*V*g = Tair - Tw Solve for V: V = (Tair - Tw)/(rho_w*g) From dry experiment force balance, find mass: m = Tair/g And use definition of density: rho_obj = m/V rho_obj = (Tair/g)/((Tair - Tw)/(rho_w*g)) = rho_w*Tair/(Tair - Tw) Summary: A) B = Tair - Tw B) V = (Tair - Tw)/(rho_w*g) C) rho_obj = rho_w*Tair/(Tair - Tw) Data: rho_w:=1000 kg/m^3; Tair:=5 Newtons; Tw:=3 Newtons; g:=9.8 N/kg; Results: A) B = 2 Newtons B) V = 204.1 mL C) rho_obj = 2500 kg/m^3 D) the absolute pressure would decrease because the height of the water surface would drop due to less water displaced

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