For a particle in uniform circular motion, the acceleration $\overrightarrow{a}$ at a point $P(R\text{,} \theta )$ on the circle of radius $R$ is (here, $\theta$ is measured from the $x$-axis),

A point $P$ moves in counter-clockwise direction on a circular path as shown in the figure. The movement of $P$ is such that it sweeps out a length $s=t^3+5$, where $s$ is in metres and $t$ is in seconds. The radius of the path is $20 \mathrm{m}$. The acceleration of $P$ when $t=2 \mathrm{s}$ is nearly,

A wire which passes through the hole in a small bead is bent in the form of quarter of a circle. The wire is fixed vertically on ground as shown in the figure. The bead is released from near the top of the wire and it slides along the wire without friction. As the bead moves from $A$ to $B,$ the force it applies on the wire is