An object weighs 275 N when fully immersed in water and 325 N when fully immersed in oil of specific gravity 0.9. The volume of the object (m3) is most nearly:

V = 0.05 m^3

Explanation:

The weight of the object of mass (m) and volume (V) in water is: 275 N and it is calculated using the buoyancy formula:

275 N = m g - V (dw) g

where (dw) is the density of water (1000 kg/m^3)

The weight of the object in oil is 325 N and it is calculated using the buoyancy formula as:

325 N = m g - V (do) g

where "do" is the density of oil which is: 0.9 x 1000 kg/m^3 = 900 kg/m^3

Therefore, subtracting term by term the two equations:

325 N -275 N = mg - mg - V (do) g + V (dw) g

50 N = V g  (dw - do)

50 N = V g (1000 - 900)

50 N = V g (100)

solving for V (which will result in units of m^3):

V = 50 / 981   m^3

V = 0.05 m^3

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

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