On a winter day a child of mass 20.0 kg slides on a horizontal sidewalk covered in ice. Initially she is moving at 3.00 m>s, but due to friction she comes to a halt in 2.25 m. What is the magnitude of the constant friction force that acts on her as she slides

An air standard cycle with variable specific heats is executed in a closed system and is composed of the following four processes. 1-2 isentropic compression 100 kpa and 22°c to 600 kpa 2-3 v=constant heat addition to 1500 k 3-4 isentropic expansion to 100 kpa 4-1 p=constant heat rejection to initial state (a) show the cycle on p-v and t-s s (b) calculate the net work output per unit mass (409 kj/kg) (c) determine the thermal efficiency (47.9%)