The acceleration vector of a particle in uniform circular motion averaged over the cycle is a null vector. This statement is

A particle of mass $m$ moves with constant speed $v$ on a circular path of radius $r$ as shown in figure. The average force on it during its motion from $A$ to $B$ is

Figure shows two cases. In first case a spring (spring constant $K$) is pulled slowly by two equal and opposite forces $F$ at both ends and in second case is pulled by a force $F$ At one end. Extensions $\left(x\right)$ In the springs will be