determination of an unknown mass (Practice the caculation of Incentainly)

set up the equipment as shown bleow

Measure both side of the angle and read the scales.

Measurement shown in the picture bleow.

θ1=44°±2°    F1=4.7N±0.5N

θ2=52°±2°    F1=5.5N±0.5N

Mass of the unknow is 

m= (cos(θ1）*F1+cos(θ2)*F2)/g

m= (cos(44°）*4.7+cos(52°)*5.5)/g

dm=|sin(θ1)F1/g|*dθ+|sin(θ2)F2/g|*dθ+|cos(θ1)/g|*dF+|cos(θ2)/g|*dF

m=0.6905kg±0.09518kg