The mobile is in equilibrium. Object B has a mass of 0.748kg. Determine the masses of objects A, C, and D. (neglect the mass of the crossbars)

See the attachment and solve question 5th

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?

Which of the following can enter and exit a closed system? a. matter and energy b. neither energy nor matter c. matter but not energy d. enrgy but not matter