A house has well-insulated walls. It contains a volume of 100 m3m3 of air at 300 K. If the energy required to lift an object of mass m through a height of 2.00 m equals the energy required to increase the temperature of this air by 1.00∘∘C., what is the value of m? (CP=72R)

A stone tied to the end of a string 80 cm long is whirled in a horizontal circle with a constant speed. If the stone makes 14 revolutions in 25 s, what is the magnitude and direction of acceleration of the stone ?