The child is pulled up to the tree limb C by a man at A walking backward. The man starts from rest when xA = 0, and moves backward with a constant acceleration aA = 0.2 m/s 2 . Neglect the size of the tree limb. When xA = 0, yB = 8m so that A and B are coincident, i. e., the rope is 16 m long. What is the speed of the boy at the instant yB = 4m ?

Two kilograms of air within a piston–cylinder assembly executes a carnot power cycle with maximum and minimum temperatures of 800 k and 300 k, respectively. the heat transfer to the air during the isothermal expansion is 60 kj. at the end of the isothermal expansion the volume is 0.4 m3. assume the ideal gas model for the air. determine the thermal efficiency, the volume at the beginning of the isothermal expansion, in m3, and the work during the adiabatic expansion, in kj.