A box contains machinery that can rotate. The total mass of the box plus the mac

Question

A box contains machinery that can rotate. The total mass of the box plus the machinery is 7 kg. A string wound around the machinery comes out through a small hole in the top of the box. Initially the box sits on the ground, and the machinery inside is not rotating (left diagram). Then you pull upwards on the string with a force of constant magnitude 119 N. At an instant when you have pulled 0.57 m of string out of the box (indicated as d on the diagram), the box has risen a distance of 0.23 m (indicated as h on the diagram), and the machinery inside is rotating.

POINT PARTICLE SYSTEM
Check all the forms of energy that change for the point particle system during this process: (can be more than one!)

Explanation / Answer

Anyway, assume when you have pulled 0.57m, all work done is just converted torotational kinetic energyof the machinery.
then rotational KE =119*0.57=67.83J

From 0.57m to 0.80m, assume all work done gets converted topotential energyandtranslational kinetic energy.

work done during lifting=0.23*119 =27.37J
potential energy=mgh=9*g*0.23=20.3067 J (g=9.8m/s2)
Translational KE= work done during lifting- potential energy=7.0633

1) What is the total kinetic energy of the system?
67.21+18.522=85.732J
2) What is the rotational kinetic energy of the machinery inside the box?
67.21J

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