Answer to Question 1
Radiation is the predominant pathway for energy loss through windows. Both
conduction and convection play roles (see Extension 9.4), but these are less important to
heat loss than radiative losses through the windowpanes.
Answer to Question 2
The weight of the piano is 2500 kg x 10 m/s2 = 25,000 N. To lift the piano 3 m,
an amount of work 25,000 N x 3 m = 75,000 J must be done. The maximum amount of
work that can be done by the 375 N force raised through 20 m is 375 N x 20 m = 7,500 J.
This is far too little to do the work to raise the piano.
The piano can only be made to raise at most by 0.3 m, because 25,000 N x 0.3 m = 7,500
J.