a heat engine extracts 55 kJ of heat from the hot reservoir each cycle and exhausts 40 kJ of heat. what are (a) the thermal efficiency and (b) the work done per cycle?

Aman is trying to drag a small tree that he cut down. if the static coefficient of friction of the tree on the ground is 0.5 and the tree weighs 670 n, what is the minimum amount of horizontal force that the man will need to apply so that the tree will start moving? o a. 465 n o b. 230 n o c. 670 n o d. 335 n