11th Class Physics Systems Of Particles & Rotational Motion / कणों के निकाय तथा घूर्णी गति Question Bank

done 11th CBSE Physics Rotational Motion Total Questions - 87

• question_answer1)
  Can centre of mass of a body coincide with the geometrical centre of the body?
  View Solution play_arrow

• question_answer2)
  A person is sitting in the compartment of a train moving with uniform velocity on a smooth track. How will the velocity of centre of mass of compartment change if the person begins to run in the compartment?
  View Solution play_arrow

• question_answer3)
  An isolated particle of mass m is moving in a horizontal plane \[(x,-y)\] along the x-axis at a certain height above the ground. It explodes suddenly into two fragments of masses m/4 and 3 m/4. An instant later, the smaller fragment is at y = + 15 cm. What is the position of larger fragment at this instant?
  View Solution play_arrow

• question_answer4)
  If a body is rotating, is it necessarily being acted upon by an external torque?
  View Solution play_arrow

• question_answer5)
  Why is the handle of a screw made wide?
  View Solution play_arrow

• question_answer6)
  A particle is moving along a straight line parallel to x-axis with constant velocity. Does its angular momentum about the origin decrease with time or increase with time or remain constant?
  View Solution play_arrow

• question_answer7)
  A particle performs uniform circular motion with an angular momentum L. If the frequency of particle's motion is doubled and its K.E. is halved, what happens to its angular momentum?
  View Solution play_arrow

• question_answer8)
  For a given mass and size, moment of inertia of a solid disc is smaller than that of a ring. Why?
  View Solution play_arrow

• question_answer9)
  In a fly wheel, most of the mass is concentrated at the rim? Explain why?
  View Solution play_arrow

• question_answer10)
  Two satellites of equal masses, which can be considered as particles are orbiting the earth at different heights. Will their moments of inertia be same or different?
  View Solution play_arrow

• question_answer11)
  How will you distinguish between a hard boiled egg and a raw egg by spinning each on a table top?
  View Solution play_arrow

• question_answer12)
  If earth were to shrink suddenly, what would happen to the length of the day?
  View Solution play_arrow

• question_answer13)
  Two discs of same mass and thickness are made of materials having different densities. Which one of them will have larger moment of inertia?
  View Solution play_arrow

• question_answer14)
  The moment of inertia of two rotating bodies A and B are \[{{I}_{A}}\] and \[{{I}_{B}}\] . \[({{I}_{A}}>{{I}_{B}})\] and their angular momenta are equal. Which one has greater K.E.?
  View Solution play_arrow

• question_answer15)
  If the ice on the polar caps of the earth melts, how will it affect the duration of the day? Explain.
  View Solution play_arrow

• question_answer16)
  A planet revolves around a massive star in a highly elliptical orbit. Is its angular momentum constant over the entire orbit?
  View Solution play_arrow

• question_answer17)
  If no external torque acts on a body, will its angular velocity remain conserved?
  View Solution play_arrow

• question_answer18)
  How does an ice-skater, a ballet dancer or an acrobat take advantage of the principle of conservation of angular momentum?
  View Solution play_arrow

• question_answer19)
  Explain why the speed of a whirl wind in a tornado is alarmingly high?
  View Solution play_arrow

• question_answer20)
  Explain how is a cat able to land on its feet after a fall taking advantage of the principle of conservation of angular momentum?
  View Solution play_arrow

• question_answer21)
  If angular momentum is conserved in a system whose moment of inertia is decreased, will its rotational kinetic energy be also conserved?  
  View Solution play_arrow

• question_answer22)
  When there is no external torque acting on a rotating body, which of the following quantities can change? (i) Angular acceleration (ii) Angular momentum (iii) Angular speed.
  View Solution play_arrow

• question_answer23)
  Equal torques are applied on a cylinder and a hollow sphere. Both have same mass and radius. The cylinder rotates about its axis and the sphere rotates about one of its diameters. Which will acquire greater speed? Explain.
  View Solution play_arrow

• question_answer24)
  A solid sphere is made to roll down from the same height on two inclined planes having different angles of inclination. In which case will it take less time to reach the bottom?
  View Solution play_arrow

• question_answer25)
  A thin wheel can stay upright on its rim for a considerable length of time when rolled with considerable velocity, while it falls from its upright position at the slightest disturbance, when stationary. Explain.
  View Solution play_arrow

• question_answer26)
  Two identical cylinders 'run a race' starting from rest at the top of an inclined plane, one slides without rolling and other rolls without slipping. Assuming that no mechanical energy is dissipated in heat, which one will win?
  View Solution play_arrow

• question_answer27)
  A one kg ball rolling on a smooth horizontal surface at\[20m{{s}^{-1}}\] comes to the bottom of an inclined plane making an angle of\[{{30}^{o}}\] with the horizontal. Calculate K.E. of the ball when it is at the bottom of incline. How far up the incline will the ball roll? Neglect friction.
  View Solution play_arrow

• question_answer28)
  A very small particle rests on the top of a hemisphere of radius 20 cm. Calculate the smallest horizontal velocity to be given to it if it is to leave the hemisphere without sliding down its surface, take \[g=9.8\,m/{{s}^{2}}\].
  View Solution play_arrow

• question_answer29)
  A ring, a disc and a sphere all of the same radius and same mass roll down an inclined plane from the same height h. Which of the three reaches the bottom (i) earliest (ii) latest?
  View Solution play_arrow

• question_answer30)
  Two forces 50 N and 100 N are acting on a rod capable of rotating it about 0 as shown in Mg. 5(HT).l What is the net torque acting on the rod?       
  View Solution play_arrow

• question_answer31)
  A small object of uniform density rolls up a curved surface with an initial velocity \[\upsilon \]. It reaches upto a maximum height of \[\frac{3{{\upsilon }^{2}}}{4g}\] with respect to the initial position. Name the given object.
  View Solution play_arrow

• question_answer32)
  A circular plate of uniform thickness has a diameter of 56 cm. A circular portion of diameter 42 cm is removed from the edge of the plate as shown in Fig. 5(HT).3. Find the position of centre of mass of the remaining portion.
  View Solution play_arrow

• question_answer33)
  A stone of mass m tied to the end of a string is whirled around in a horizontal circle (neglect force due to gravity). The length of the string is reduced gradually keeping the angular momentum of the stone about the centre of the circle constant. Then the tension in the string is given by  \[T=A{{r}^{n}}\], where A is a constant and r is instantaneous radius of the circle. Show that n = - 3.
  View Solution play_arrow

• question_answer34)
  A threaded rod with 12 turns/cm and diameter 1.18 cm is mounted horizontally. A bar with a threaded hole to match the rod is screwed onto the rod. The bar spins at 216 rev/min. How long will it take for the bar to move 1.50 cm along the rod?
  View Solution play_arrow

• question_answer35)
  Find the centre of mass of a uniform disc of radius a from which a circular section of .radius b has been removed. The centre of hole is at a distance c from the centre of the disc.
  View Solution play_arrow

• question_answer36)
  A solid cylinder of mass 20 kg and radius 0-12 m rotating with initial angular speed of 125 rad/s is placed lightly (Le. without any translational push) on a horizontal table with coefficient of kinetic friction \[{{\mu }_{k}}=0.15\]  between the cylinder and the table. (a) After how long does the cylinder start rolling? (b) What is the initial translational energy, rotational energy and total energy of the cylinder? (c) What is the final (i.e. after rolling begins) translational energy, rotational energy and total energy of the cylinder? (d) Is the final total energy equal to the initial total energy of motion of the cylinder? If not, where does the difference of energy disappear? (e) Account for the loss of total energy of motion in the following way: find the work done by friction on the body for its translational motion. Show that net work done by friction on the body is negative equal in magnitude to the loss of total energy calculated in (d) above.
  View Solution play_arrow

• question_answer37)
  Point masses \[{{m}_{1}}\] and \[{{m}_{2}}\] are placed at the opposite ends of a rigid rod of length L, and negligible mass. The rod is to be set rotating about an axis perpendicular to it. Find the position on this rod through which the axis should pass in order that the work required to set the rod rotating with angular velocity \[{{\omega }_{0}}\] should be minimum.              
  View Solution play_arrow

• question_answer38)
  A ball of mass \[{{10}^{-2}}kg\] and having charge + \[3\times {{10}^{-6}}C\]is tied at one end of a 1 m long thread. The other end of the thread is fixed and a charge - \[3\times {{10}^{-6}}C\]is placed at this end. The ball can move in the circular orbit of radius 1 m in the vertical plane. Initially, the ball is at the bottom. Find the minimum initial horizontal velocity of the bally so that it will be able to complete the full circle.
  View Solution play_arrow

• question_answer39)
  A particle describes a horizontal circle on the smooth inner surface of a conical funnel as shown in Fig. 5(HT).7. If the height of the plane of the circle above the vertex is 9-8 cm, find the speed of the particle.
  View Solution play_arrow

• question_answer40)
  Three particles, each of mass m are situated at the vertices of an equilateral triangle of side a. The only forces acting on the particles are their mutual gravitational forces. It is desired that each particle move in a circle, while maintaining the original mutual separation a. Find the initial velocity that should be given to each particle and also the time period of the circular motion.
  View Solution play_arrow

• question_answer41)
  From a uniform circular disc of diameter d, a circular disc of diameter d/6 and having centre at a distance d/4 from the centre of the disc is scooped out. Determine the centre of mass of remaining portion.
  View Solution play_arrow

• question_answer42)
  A spot light S rotates in a horizontal plane with a constant angular velocity of 0.1 rad/s. The spot of light P moves along the wall at a distance 3 m. What is the velocity of the spot P when\[\text{ }\!\!\theta\!\!\text{ }=\text{ 45}{}^\circ \]?
  View Solution play_arrow

• question_answer43)
  A nail is located at a certain distance vertically below the point of suspension of a simple pendulum. The pendulum bob is released from a position where the string makes an angle of \[\text{6}0{}^\circ \] with the vertical. Calculate the distance of nail from the point of suspension such that the bob will just perform revolutions with the nail as centre. Assume the length of the pendulum to be one meter.
  View Solution play_arrow

• question_answer44)
  A uniform sphere of mass m and radius R is placed on a rough horizontal surface. The sphere is struck horizontally at a height h from the floor. Show that the sphere rolls without slipping with a constant velocity, when h = 7 R/5.
  View Solution play_arrow

• question_answer45)
  A carpet of mass M is rolled along its length so as to form a cylinder of radius R and is kept on a rough floor. When a negligibly small push is given to the cylindrical carpet, it starts unrolling itself without sliding on the floor. Calculate horizontal velocity of cylindrical part of the carpet when its radius reduces to \[R/2\].
  View Solution play_arrow

• question_answer46)
  Where does the centre of mass of a uniform triangular lamina lie?
  View Solution play_arrow

• question_answer47)
  Can a body in translatory motion have angular momentum? Explain.
  View Solution play_arrow

• question_answer48)
  The length of seconds hand of a clock is 10 cm. The speed of the tip of the hand is..........
  View Solution play_arrow

• question_answer49)
  Is torque a scalar or vector? If it is a vector, what rule is used to determine its direction?
  View Solution play_arrow

• question_answer50)
  Why do we prefer to use a wrench with a long arm?
  View Solution play_arrow

• question_answer51)
  What is the dimensional formula of angular momentum and what are its units? Is it a scalar?
  View Solution play_arrow

• question_answer52)
  Is the angular speed of rotation of hour hand of a watch greater or smaller than the angular velocity of earth's rotation about its axis?
  View Solution play_arrow

• question_answer53)
  In which of the following cases shown in Fig. 5(b).28, it is most difficult to rotate the rod? Explain why?
  View Solution play_arrow

• question_answer54)
  There is a stick half of which is wooden and half is of steel. It is pivoted at the wooden end and a force is applied at the steel end at right angles to its length. Next, it is pivoted at the steel end and the same force is applied at the wooden end. In which case is angular acceleration more and why?
  View Solution play_arrow

• question_answer55)
  Two circular discs A and B of the same mass and same thickness are made of two different metals whose densities are\[{{d}_{A}}\] and\[{{d}_{B}}\left( {{d}_{A}}>{{d}_{B}} \right)\] . Their moments of inertia about eh axes passing through their centres of gravity and perpendicular to their planes are\[{{I}_{A}}\] and\[{{I}_{B}}\]. Which is greater, \[{{I}_{A}}\]or\[{{I}_{B}}\]?
  View Solution play_arrow

• question_answer56)
  Calculate radius of gyration of a cylindrical rod of mass m and length L about an axis of rotation perpendicular to its length and passing through the centre.
  View Solution play_arrow

• question_answer57)
  (i) A person sits near the edge of a circular platform revolving with a uniform angular speed. What will be the change in the motion of the platform? (ii) What if the person starts moving from the edge towards the centre of the platform?
  View Solution play_arrow

• question_answer58)
  Why there are two propellers in a helicopter?
  View Solution play_arrow

• question_answer59)
  A solid wooden sphere rolls down two different inclined planes of the same height but of different inclinations. (a) Will it reach the bottom with same speed in each case? (b) Will it take longer to roll down one inclined plane than other? Explain.
  View Solution play_arrow

• question_answer60)
  Using expressions for power and kinetic energy of rotational motion, derive the relation \[\tau =I\alpha \], Where letters have their usual meaning.
  View Solution play_arrow

• question_answer61)
  A thin uniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane with an angular velocity \[\omega \]. Another disc of the same dimensions but of mass M/4 is placed gently on the first disc co-axially. Show that angular velocity of the system is \[4\omega /5\].
  View Solution play_arrow

• question_answer62)
  What is the position vector of centre of mass of two particles of equal masses?
  View Solution play_arrow

• question_answer63)
  If one of the particles is heavier than the other, to which side will their centre of mass shift?
  View Solution play_arrow

• question_answer64)
  Does centre of mass of a system of two particles lie on the line joining the particles?              
  View Solution play_arrow

• question_answer65)
  Can centre of mass of a body lie where there is absolutely no mass?                          
  View Solution play_arrow

• question_answer66)
  Can centre of mass of a body coincide with geometrical centre of the body?                
  View Solution play_arrow

• question_answer67)
  Does centre of mass of a rigid body lie always on the body?                     
  View Solution play_arrow

• question_answer68)
  Which physical quantity is represented by the product of the moment of inertia and the angular velocity?
  View Solution play_arrow

• question_answer69)
  What is an isolated system?                                                                         
  View Solution play_arrow

• question_answer70)
  Which component of linear momentum does not contribute to angular momentum :
  View Solution play_arrow

• question_answer71)
  What physical quantities are expressed by the following? (i) Moment of linear momentum (ii) Rate of change of angular momentum.
  View Solution play_arrow

• question_answer72)
  A ring and a circular disc of different materials have equal masses and equal radii. Which one will have a larger moment of inertia about an axis passing through its centre of mass perpendicular to its plane?
  View Solution play_arrow

• question_answer73)
  A disc of metal is melted and recast in the form of a solid sphere. What will happen to the moment of inertia about a vertical axis passing through the centre? 
  View Solution play_arrow

• question_answer74)
  What are the units and dimensions of moment of inertia? Is it a vector?
  View Solution play_arrow

• question_answer75)
  What is rotational analogue of mass of a body?
  View Solution play_arrow

• question_answer76)
  What are the two theorems of moment of inertia?
  View Solution play_arrow

• question_answer77)
  What is moment of inertia of a solid sphere about its diameter?
  View Solution play_arrow

• question_answer78)
  What is moment of inertia of a hollow sphere about an axis passing through its centre.
  View Solution play_arrow

• question_answer79)
  What are the factors on which moment of inertia of a body depend?
  View Solution play_arrow

• question_answer80)
  Is radius of gyration of a body constant quantity?
  View Solution play_arrow

• question_answer81)
  There are two spheres of same mass and same radius, one is solid and other is hollow. Which of them has a larger moment of inertia about its diameter?
  View Solution play_arrow

• question_answer82)
  Two solid spheres of the same mass are made of metals of different densities. Which of them has a larger moment of inertia about a diameter?
  View Solution play_arrow

• question_answer83)
  What is rotational analogue of force?
  View Solution play_arrow

• question_answer84)
  A cannon ball and a marble ball roll from rest down an incline. Which goes to the bottom first?
  View Solution play_arrow

• question_answer85)
  A ballet-dancer stretches her hands out for slowing down. This is based on principle of conservation of..
  View Solution play_arrow

• question_answer86)
  Can a body in translatory motion have angular momentum?
  View Solution play_arrow

• question_answer87)
  Why spin angular velocity of a star is greatly enhanced when it collapses under gravitational pull and becomes a neutron star?
  View Solution play_arrow