The composite wall of an oven consists of three materials, two of which are of known thermal conductivity, kA = 25 W/m ⋅ K and kC = 60 W/m ⋅ K, and known thickness, LA = 0.40 m and LC = 0.20 m. The third material, B, which is sandwiched between materials A and C, is of known thickness, LB = 0.20 m, but unknown thermal conductivity kB. Under steady-state operating conditions, measurements reveal an outer surface temperature of Ts, o=20, an inner surface temperature of Ts, i=600°C, and an oven air temperature of T[infinity]=800°C. The inside convection coefficient h is known to be 25W/m^2⋅K. What is the value of kB?

Answer: fn = wcos50 = 38.89(9.81)(cos50) = 245.23 n

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.