The resultant of two forces,one double the other in magnitude,is perpendicular to the smaller of the two forces. The angle between the two forces is ........ $^o$

$A$ ladder rests against a frictionless vertical wall,with its upper end $6 \, m$ above the ground and the lower end $4 \, m$ away from the wall. The weight of the ladder is $500 \, N$ and its center of gravity ($C$.$G$.) is at $1/3$ of its length from the lower end. The reaction force from the wall will be (in Newton):

$A$ body of mass $1 \ kg$ is suspended with the help of two strings making angles as shown in the figure. The magnitudes of tensions $T_1$ and $T_2$,respectively,are (in $N$):

$A$ flexible chain of mass $m$ hangs between two fixed points at the same level. The inclination of the chain with the horizontal at the two points of support is $30^{\circ}$. Considering the equilibrium of each half of the chain, the tension of the chain at the lowest point is . . . . . . .

Three blocks are placed as shown in the figure. The masses of $A$,$B$,and $C$ are $m_1$,$m_2$,and $m_3$ respectively. The force exerted by block $C$ on block $B$ is .........

An object is in equilibrium when four concurrent forces,acting in the same plane,are in the directions shown in the figure. Find the magnitudes of $F_1$ and $F_2$.