A disk of radius 0.20 m can rotate about its fixed central axis without friction. Two strings are wound around the rim in opposite directions. String A is pulled with a constant tension of 6.0 N over the angular interval from 0 rad to 1.5 rad. String B is pulled simultaneously with a constant tension of 4.0 N over the interval from 0.50 rad to 2.0 rad. Treat each string’s tension as producing a tangential force at the rim and neglect the masses of the strings.
(a) Describe how you would determine the work done on the disk by the tension in each string individually. Include the relationship between the relevant physical quantities in your explanation.
(b) Qualitatively explain whether the two tensions always aid, always oppose, or partly cancel each other’s rotational effect during the motion described.
(c) Calculate the net work delivered to the disk over the full 0 rad → 2.0 rad motion. Express your answer with appropriate units and sign.
(d) Interpret the sign of your result from part (c) in terms of the energy transfer to or from the disk.