A ball of mass \(0.1~\text{kg}\) is whirled in a horizontal circle of radius \(1\) m by means of a string at an initial speed of \(10~\text{rpm}\) . Keeping the radius constant, the tension in the string is reduced to one quarter of its initial value. The new speed is:

1.	\(5~\text{rpm}\)	2.	\(10~\text{rpm}\)
3.	\(20~\text{rpm}\)	4.	\(14~\text{rpm}\)

A cyclist riding the bicycle at a speed of $14\sqrt{3}$ms^–1 takes a turn around a circular road of radius $20\sqrt{3}$m without skidding. Given g = 9.8 ms^–2, what is his inclination to the vertical?

1. 30^o

2. 90^o

3. 45^o

4. 60^o

A point mass \(m\) is suspended from a light thread of length \(l,\) fixed at \(O\), and is whirled in a horizontal circle at a constant speed as shown. From your point of view, stationary with respect to the mass, the forces on the mass are:

1.		2.
3.		4.

If a cyclist moving with a speed of 4.9 m/s on a level road can take a sharp circular turn of radius 4 m, then coefficient of friction between the cycle tyres and road is 

1. 0.41

2. 0.51

3. 0.61

4. 0.71

A motor cycle driver doubles its velocity when he is having a turn. The force exerted outwardly will be

1. Double

2. Half

3. 4 times

4. $\frac{1}{4}$ times

Two bodies of equal masses revolve in circular orbits of radii R₁ and R₂ with the same period. Their centripetal forces are in the ratio

(1) ${\left(\frac{{\displaystyle R_2}}{{\displaystyle R_1}}\right)}^2$

(2) $\frac{R_1}{R_2}$

(3) ${\left(\frac{{\displaystyle R_1}}{{\displaystyle R_2}}\right)}^2$

(4) $\sqrt{R_1{R}_2}$

A mass is supported on a frictionless horizontal surface. It is attached to a string and rotates about a fixed centre at an angular velocity ω₀. If the length of the string and angular velocity are doubled, the tension in the string which was initially T₀ is now 

1. T₀

2. T₀/2

3. 4 T₀

4. 8 T₀

Three identical particles are joined together by a thread as shown in figure. All the three particles are moving in horizontal circles centred at O. If the velocity of the outermost particle is v₀, then the ratio of tensions in the three sections of the string is 

1. 3 : 5 : 7

2. 3 : 4 : 5

3. 7 : 11 : 6

4. 3 : 5 : 6

A block of mass m at the end of a string is whirled round in a vertical circle of radius R. The critical speed of the block at the top of its swing below which the string would slacken before the block reaches the top is 

1. Rg

2. (Rg)²

3. R/g

4. $\sqrt{Rg}$

A bucket tied at the end of a 1.6 m long string is whirled in a vertical circle with constant speed. What should be the minimum speed so that the water from the bucket does not spill, when the bucket is at the highest position (Take g = 10 m/s²) 

1. 4 m/sec

2. 6.25 m/sec

3. 16 m/sec

4. None of the above