Determining scale readings given different densities

[heyrefusuck]

Connected by a string to a scale is an object and when suspended in air, the scale reads 200 N. The scale reads 150 N when the object is suspended in water (d = 1000 kg/m^3). What does the scale read (in N) when the object is suspended in oil having a density of 800 kg/m^3?

I determined that the volume of the object was .015 m^3 from using the d=m/v formula in the H2O portion of the problem. I just substituted the volume into the oil density and determined that the mass was 12.24 kg. and then converted that to 120 N. Did I do this correctly?

 

[rl.bhat]

I determined that the volume of the object was .015 m^3 from using the d=m/v formula in the H2O portion of the problem.

Loss of weight in liquid is equal to the weight of the displaced liquid.
In the problem loss of weight in water is 50N. Then what is the volume of the object?

 

[nlightner]

Yes, your approach to solving this problem is correct. By using the density formula and substituting in the given values, you were able to determine the mass of the object in the oil. Then, by using the equation F = mg, where F is the force measured by the scale, m is the mass of the object, and g is the acceleration due to gravity, you were able to calculate the scale reading in N. Keep up the good work!