Approximate the gravitational force of attraction between a 50.0 kg girl and a 66.0 kg boy if they are sitting 2.0 m apart in physics class. ___N

*Notice how small the answer is. The boy and girl are certainly not very attracted to each other. This is why the gravitational force between objects is normally ignored when drawing free-body diagrams. The force of gravity is incredibly small unless a very, very large mass is involved (e. g. a planet).

I) a gas contained within a piston-cylinder assembly undergoes two processes, a and b, between the same end states, 1 and 2, where p1 = 10 bar, v1 = 0.1 m3 , u1 = 400 kj and p2 = 1 bar, v2 = 1.0 m3 , u2 = 200 kj: ' process a: process from 1 to 2 during which the pressure-volume relation is pv = constant. ' process b: constant-volume process from state 1 to a pressure of 2 bar, followed by a linear pressure-volume process to state 2. kinetic and potential energy effects can be ignored. for each of the processes a and b, a) sketch the process on a p-v diagram. b) evaluate the work, in kj. c) evaluate the heat transfer, in kj.(ans : qb,12 = -65.0 kj)