How does the kinetic model develop a root mean square velocity? What is root mean square? Half the class average the numbers below, square the average, then take the square root of the squared averages. Half the class square the numbers below, average the squares then take the square root. 2.1, 3.5, 4.0, 5.1, 6.5, 7.0

 Large number of molecules of identical mass, m, which behave as point particles  Molecules move randomly and obey Newton’s Laws of motion  Molecules are, far apart on average & are small compared to their relative separations.  When molecules collide or hit walls they  bounce elastically  And no time is spent in collisions

 When molecules bounce off walls Δmv due to change in direction.  There must be a force on molecules from wall (Newton’s II Law).  There must be an equal and opposite force on wall from molecules (Newton’s III Law).  Each time there is a collision between molecules & wall, a force is exerted on wall.  Average of all microscopic forces on the wall over time means there is effectively a constant force on the wall.

 676/root_mean_square_speed_3.JPG?size=be stfit&width=337&height=312&revision=1 676/root_mean_square_speed_3.JPG?size=be stfit&width=337&height=312&revision=1 