$A$ wheel is subjected to uniform angular acceleration about its axis. Initially,its angular velocity is zero. In the first $2 \ s$,it rotates through an angle ${\theta _1}$. In the next $2 \ s$,it rotates through an additional angle ${\theta _2}$. The ratio of ${\theta _2}/{\theta _1}$ is:

The ratio of angular speeds of the minute hand and the hour hand of a watch is:

If the frequency of an object in uniform circular motion is doubled,its acceleration becomes

An electric fan has blades of length $30 \, cm$ as measured from the axis of rotation. If the fan is rotating at $1200 \, r.p.m.$,the acceleration of a point on the tip of the blade is about .......... $m/s^2$.

$A$ racing car is travelling along a track at a constant speed of $40\ m/s$. $A$ $T.V.$ cameraman is recording the event from a distance of $30\ m$ directly away from the track as shown in the figure. In order to keep the car under view in the position shown,the angular speed with which the camera should be rotated is ........ $rad/s$.

$A$ particle of mass $10 \text{ g}$ moves along a circle of radius $6.4 \text{ cm}$ with a constant tangential acceleration. If the kinetic energy of the particle becomes $8 \times 10^{-4} \text{ J}$ by the end of the second revolution after the beginning of the motion, the magnitude of the tangential acceleration is (in $\text{ m/s}^2$)