If the overbridge is concave instead of being convex, the thrust on the road at the lowest position will be

(1) $mg+\frac{m{v}^2}{r}$

(2) $mg-\frac{m{v}^2}{r}$

(3) $\frac{m^2{v}^{2}g}{r}$

(4) $\frac{v^{2}g}{r}$

A motor cyclist moving with a velocity of 72 km/hour on a flat road takes a turn on the road at a point where the radius of curvature of the road is 20 meters. The acceleration due to gravity is 10 m/sec². In order to avoid skidding, he must not bend with respect to the vertical plane by an angle greater than 

(1) $\theta ={\tan }^{-1}6$

(2) $\theta ={\tan }^{-1}2$

(3) $\theta ={\tan }^{-1}25.92$

(4) $\theta ={\tan }^{-1}4$

A particle moves in a circular orbit under the action of a central attractive force inversely proportional to the distance ‘r’. The speed of the particle is 

(1) Proportional to r²

(2) Independent of r

(3) Proportional to r

(4) Proportional to 1/r

Two masses M and m are attached to a vertical axis by weightless threads of combined length l. They are set in rotational motion in a horizontal plane about this axis with constant angular velocity ω. If the tensions in the threads are the same during motion, the distance 'x' of M from the axis is- 

(1) $\frac{Ml}{M+m}$

(2) $\frac{ml}{M+m}$

(3) $\frac{M+m}{M}l$

(4) $\frac{M+m}{m}l$

A 500 kg car takes a round turn of radius 50 m with a velocity of 36 km/hr. The centripetal force is 

(1) 250 N

(2) 750 N

(3) 1000 N

(4) 1200 N

A ball of mass 0.25 kg attached to the end of a string of length 1.96 m is moving in a horizontal circle. The string will break if the tension is more than 25 N. What is the maximum speed with which the ball can be moved 

(1) 14 m/s

(2) 3 m/s

(3) 3.92 m/s

(4) 5 m/s

A body of mass 5 kg is moving in a circle of radius 1m with an angular velocity of 2 radian/sec. The centripetal force is 

(1) 10 N

(2) 20 N

(3) 30 N

(4) 40 N

A stone of mass of 16 kg is attached to a string 144 m long and is whirled in a horizontal circle. The maximum tension the string can withstand is 16 Newton. The maximum velocity of revolution that can be given to the stone without breaking it will be-

(1) 20 ms^–1

(2) 16 ms^–1

(3) 14 ms^–1

(4) 12 ms^–1

Find the maximum velocity for skidding for a car moved on a circular track of radius 100 m. The coefficient of friction between the road and tyre is 0.2 

(1) 0.14 m/s

(2) 140 m/s

(3) 1.4 km/s

(4) 14 m/s

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