Two bodies of mass 10 kg and 5 kg moving in concentric orbits of radii R and r such that their periods are the same. Then the ratio between their centripetal acceleration is 

1. R/r

2. r/R

3. R²/r²

4. r²/R²

A particle is moving in a horizontal circle with constant speed. It has constant 

1. Velocity

2. Acceleration

3. Kinetic energy

4. Displacement

The angular speed of a flywheel making 120 revolutions/minute is: 

1. $2\pi rad/s$

2. $4{\pi }^{2}rad/s$

3. $\pi rad/s$

4. $4\pi rad/s$

Certain neutron stars are believed to be rotating at about 1 rev/sec. If such a star has a radius of 20 km, the acceleration of an object on the equator of the star will be 

1. $20\times {10}^{8}m/{\sec }^2$

2. $8\times {10}^{5}m/{\sec }^2$

3. $120\times {10}^{5}m/{\sec }^2$

4. $4\times {10}^{8}m/{\sec }^2$

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

1. 1600 m/sec²

2. 4740 m/sec²

3. 2370 m/sec²

4. 5055 m/sec²

The angular speed of seconds needle in a mechanical watch is:

1. $\frac{\pi }{30}$ rad/s

2. 2π rad/s

3. π rad/s

4. $\frac{60}{\pi }$ rad/s

A particle moves with constant speed $v$ along a circular path of radius $r$ and completes the circle in time $T$. The acceleration of the particle is:
1. $2\pi v / T$
2. $2\pi r / T$
3. $2\pi r^2 / T$
4. $2\pi v^2 / T$

          
1. $3.14~\text{m/s}$
2. $2.0~\text{m/s}$
3. $1.0~\text{m/s}$
4. zero

A stone tied to the end of a string of $1$ m long is whirled in a horizontal circle with a constant speed. If the stone makes $22$ revolutions in $44$ s, what is the magnitude and direction of acceleration of the stone?