The statement that is NOT true about the difference between laminar and turbulent boundary layers is:1.the Reynolds number for a turbulent boundary layer is higher than that for a laminar boundary layer. 2.the wall shear stress for a turbulent boundary layer is greater than that for a laminar boundary layer. 3.a turbulent boundary layer is thicker than a laminar boundary layer.4.the velocity gradient at the wall is greater for a laminar boundary layer than a turbulent boundary layer.

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.

Different types of steels contain different elements that alter the characteristics of the steel. for each of the following elements, explain what the element does when alloyed with steel.

Ifa component is made of two or more materials with different modulus of elasticity (e), it is called a composite member and we calculate the factor·n". mention the formula for calculating n". also, ifn> 1, explain what will happen to the 1. transformed.gi) ifn 1, what will happen to the material when transformed material when