apparent weight question

[ssiding]

An object with mass 30kg and specific gravity 3.6 is placed in a fluid whose specific gravity is 1.2. Neglecting viscosity, which of the following is true?
A. The acceleration of the object is 1/3 g and its apparent weight is 100N
B. the acceleration of the object is 2/3 g and its apparent weight is 100N
C. the acceleration of the object is 1/3 g and its apparent weight is 200N
D. the acceleration of the object is 2/3 g and its apparent weight is 200N


Thanks again for all the help guys

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[TieuBachHo]

Wow ... so many questions LOL.

I scratched it out to be 2/3g and 200N. So the answer is D. Just use the buoyant force (Fb) ... Fnet = mg - Fb= ma. Since the spec. grav. of object is larger than the spec. grav. of fluid, it's fully submerged in the fluid. V (object) = V (fluid). Apparent weight is just the normal force that would act against the net force if it's present. So apparent weight = Fnet = (2/3) mg = 200N