Mathematical idealization of a crane has three bars with their vertices arranged as shown in the figure with a load of $$80$$ $$kN$$ hanging vertically. The coordinates of the vertices are given in parentheses. The force in the member $$QR,\,\,{F_{QR}}$$ will be

In a beam of length $$L,$$ four possible influence line diagrams for shear force at a section located at a distance of $${L \over 4}$$ from the left end support (marked as $$P,Q,R$$ and $$S$$ ) are shown below. The correct influence line diagram is

The degree of static indeterminacy of a rigid jointed frame PQR supported as shown in the figure is

The perception-reaction time for a vehicle travelling at 90 km/h, given the coefficient of longitudinal friction of 0.35 and the stopping sight distance of 170 m (assume g = 9.81 m/s2), is _________ seconds.