The kinetic energy $k$ of a particle moving along a circle of radius $R$ depends on the distance covered $s$ as $k = as^2$ where $a$ is a constant. The force acting on the particle is

- A
$2a\frac{{{s^2}}}{R}$

- B
$2as{\left( {1 + \frac{{{s^2}}}{{{R^2}}}} \right)^{1/2}}$

- C
$2as$

- D
$2a\frac{{{R^2}}}{s}$

A string of length $0.1\,m$ cannot bear a tension more than $100\,N$. It is tied to a body of mass $100\,g$ and rotated in a horizontal circle. The maximum angular velocity can be .......... $rad/sec$

In uniform circular motion, the velocity vector and acceleration vector are

A man standing on the roof of a house of height $h$ throws one particle vertically downwards and another particle horizontally with the same velocity $u$. The ratio of their velocities when they reach the earth's surface will be

Two bodies $A$ & $B$ rotate about an axis, such that angle $\theta_A$ (in radians) covered by first body is proportional to square of time, & $\theta_B$ (in radians) covered by second body varies linearly. At $t = 0, \theta \,A = \theta \,B = 0$. If $A$ completes its first revolution in $\sqrt \pi$ sec. & $B$ needs $4\pi \,sec$. to complete half revolution then; angular velocity $\omega_A : \omega_B$ at $t = 5\, sec$. are in the ratio

The net applied force on a body in uniform circular motion should always be