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question_answer1) What is the advantage of the concept of centre of mass?
question_answer2) Should the centre of mass of a body necessarily lie inside the body?
question_answer3) Does the centre of mass of a solid necessarily lie within the body? If not, give an example.
question_answer4) Is centre of mass a reality?
question_answer5) Is it correct to say that the centre of mass of a system particles is always given by the average Position vectors of the constituent particles? If not, when is this statement true?
question_answer6) If two particles of masses \[{{m}_{1}}\] and \[{{m}_{2}}\] move velocities \[{{\upsilon }_{1}}\] and \[{{\upsilon }_{2}}\] towards each other on a smooth horizontal table, what is the velocity of their centre of mass?
question_answer7) Name the physical quantity that corresponds to the moment of force. On what factors does it depend?
question_answer8) What happens to the moment of force about a point, if the line of action of the force moves towards the point?
question_answer9) A body is in rotational motion. Is it necessary that a torque be acting on it?
question_answer10) Why do we prefer to use a wrench of longer aim?
question_answer11) Why in hand driven grinding machine, handle is put near the circumference of the stone or wheel?
question_answer12) It is difficult to open the door by pushing it or pulling it at the hinge. Why?
question_answer13) Why a force is applied at right angles to the heavy door at the outer edge while closing or opening it?
question_answer14) A man climbs a tall, old step ladder that has a tendency to sway. He feels much more unstable when standing near the top than when near the bottom. Why?
question_answer15) Why it is easier to open a tap with two fingers than with one finger?
question_answer16) A faulty balance with unequal arms has its beam horizontal. Are the weights of the two pans equal?
question_answer17) Can the couple acting on a rigid body produce translatory motion?
question_answer18) A labourer standing near the top of an old wooden step ladder feels unstable. Why?
question_answer19) Which physical quantities are expressed by the following: (i) the rate of change of angular momentum, and (ii) moment of linear momentum ?
question_answer20) If no external torque acts on a body, will its angular velocity remain conserved?
question_answer21) When a labourer cuts down a tree, he makes a cut on the side facing the direction in which he wants it to fall. Why?
question_answer22) Define the term angular impulse.
question_answer23) Which component of linear momentum does not contribute to angular momentum?
question_answer24) A particle revolves uniformly along a circular path, on a smooth horizontal table, by means of a string connected to it. Does its angular momentum change, if the string is suddenly cut?
question_answer25) A heavenly body (such as a comet) revolves around a massive star in a highly elliptical orbit. Is its angular momentum constant over the entire orbit? (Ignore any mass loss of the comet when it comes too close to the star).
question_answer26) A projectile acquires angular monies turn about the point of projection during its flight. Does it violate the conservation of angular momentum?
question_answer27) Is a body in circular motion in equilibrium?
question_answer28) When is a body lying in a gravitation field in stable equilibrium?
question_answer29) Can a body in equilibrium while in motion? If yes, give an example.
question_answer30) The bottom of a ship is made heavy. Why?
question_answer31) Why does a girl lean towards right while carrying a bag in her left hand?
question_answer32) Some heavy boxes are to be loaded along with some empty boxes on a cart. Which boxes should be put on the cart first and why?
question_answer33) Standing is not allowed in a double decker bus. Why?
question_answer34) Why we cannot rise from a chair without bending a little forward?
question_answer35) A system is in stable equilibrium. What can we say about its potential energy?
question_answer36) Why is moment of inertia also called rotational inertia?
question_answer37) Give the physical significance of moment of inertia.
question_answer38) Does moment of inertia of a body r change with the change of the axis of rotation?
question_answer39) Does the moment of inertia of a rigid body change with the speed of rotation?
question_answer40) About which axis, the moment of inertia of a body is minimum?
question_answer41) Can the mass of body be taken to be concentrated at its centre of mass for the purpose of calculating its rotational inertia?
question_answer42) About which axis would a uniform cube have a minimum rotational inertia?
question_answer43) Is radius of gyration a constant quantity?
question_answer44) Does the radius of gyration depend upon the speed of rotation of the body?
question_answer45) Two lenses of same mass and same radius are given. One is convex and other is concave. Which one will have greater moment of inertia, when rotating about an axis perpendicular to the plane and passing through the centre?
question_answer46) A disc is recast into a thin walled cylinder of same radius. Which will have large moment of inertia?
question_answer47) Two solid spheres of the same mass are made of metals of different densities. Which of them has a larger moment of inertia about the diameter? Why?
question_answer48) What is the advantage of the flywheel?
question_answer49) Why spokes are provided in a bicycle wheel?
question_answer50) Will two spheres of equal masses, one solid and the other hollow have equal moments of inertia? Give reason.
question_answer51) Why is it more difficult to revolve a stone tied to a large string than a stone tied to a smaller string?
question_answer52) 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?
question_answer53) What is the use of flywheel in railway engine?
question_answer54) There is a stick half of which is wooden is 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 the angular acceleration more and why?
question_answer55) Is the angular momentum of a system always conserved? If not, under what condition is it conserved?
question_answer56) A flywheel is revolving with a constant angular velocity. A chip of its rim breaks and flies away. What will be the effect on its angular velocity?
question_answer57) A cat is able to land on its feet after a fall. Why?
question_answer58) Why there are two propellers in a helicopter?
question_answer59) The speed of a whirl wind in a tornado is alarmingly high. Why?
question_answer60) If earth contracts to half its radius, what would be the length of the day?
question_answer61) Two boys of the same weight sit at the opposite ends of a diameter of a rotating circular table. What happens to the speed of rotation if they move nearer to the axis of rotation?
question_answer62) A thin wheel can stay up right on its rim for a considerable length of time when rolled with a considerable velocity, while it falls from its upright position at the slightest disturbance when stationary. Give reason.
question_answer63) A person is standing on a rotating table with metal spheres in his hands. If he withdraws his hands to his chest, what will be the effect on his angular velocity?
question_answer64) A circular turn table rotates at constant angular velocity about a vertical axis. There is no friction and no driving torque. An ice pan containing ice also rotates with it. The ice melts but none of the water escapes from the pan. Is the velocity now greater, the same or less than the original velocity? Give reason.
question_answer65) Many rivers flow towards the equator. What effect does the sediment they carry to the seas have on the rotation of the earth?
question_answer66) The moments 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 a greater kinetic energy?
question_answer67) If angular momentum is conserved in a system whose moment of inertia is decreased, will its rotational kinetic energy be conserved?
question_answer68) How does an ice-skater, a ballet dancer or an acrobat take advantage of the principle of conservation of angular momentum? Or How does a ballet dancer vary her angular speed by outstretching her arms and legs?
question_answer69) If earth were to shrink suddenly, what would happen to the length of the day?
question_answer70) A body A of mass M while falling vertically downwards under gravity breaks into two parts; a body B of mass M/ 3 and a body C of mass 2 M/ 3. How does the centre of mass of bodies B and C taken together shift compared to that of A?
question_answer71) Two identical particles move towards each other with velocity \[2\upsilon \] and \[\upsilon \] respectively. What is the velocity of the centre of mass?
question_answer72) A particle moves in a circular path with decreasing speed. What happens to its angular momentum?
question_answer73) A particle performing uniform circular motion has angular momentum L. What will be the new angular momentum, if its angular frequency is doubled and its kinetic energy halved?
question_answer74) The angular velocity of the earth around the sun increases, when it comes closer to the sun. Why?
question_answer75) Why are we not able to rotate a wheel by pulling or pushing along its radius?
question_answer76) Two solid spheres of the same mass are made of metals of different densities. Which of them has larger moment of inertia about its diameter?
question_answer77) A planet revolves around a massive star in a highly elliptical orbit. Is the angular momentum constant over the entire orbit?
question_answer78) If no external torque acts on a body, will its angular velocity remain constant? Give reason.
question_answer79) "Newton's laws of motion are applicable to individual particles". How would you explain the motion of a large body?
question_answer80) If an external force can change the state of motion of CM of a body, how does the internal force of the brakes bring a car to rest?
question_answer81) Two men stand facing each other on two boats floating on still water at a distance apart. A rope is held at its ends by both. The two boats are found to meet always at the same point, whether each man pulls separately or both pull together, why? Will the time taken be different in the two cases? Neglect friction.
question_answer82) Prove that the centre of mass of two particles divides the line joining the particles in the inverse ratio of their masses.
question_answer83) Two balls of mass m each are placed at the two vertices of an equilateral triangle. Another ball of mass 2m is placed at the third vertex of the triangle. Locate the centre of mass of the system.
question_answer84) What is the difference between centre of gravity and centre of mass?
question_answer85) There are 100 passengers in a stationary railway compartment. A physical fight starts between the passengers over some difference of opinion, (i) Will the position of CM of the compartment change? (ii) Will the position of CM of system (compartment +100 passengers) change? Give reason.
question_answer86) Show that moment of a couple does not depend on the point about which you take the moments.
question_answer87) Show that the angular momentum about any point of a single particle moving with constant velocity remains constant throughout the motion. Is there any external torque on the particle?
question_answer88) A rod of weight W is supported by two parallel edges A and B and is in equilibrium in horizontal position. The knives are at a distance d from each other. The centre of mass of the rod is at distance \[x\] from A. Find the normal reactions at the knife edges A and B.
question_answer89) Torque and work are both equal to force times distance. Then how do they differ?
question_answer90) When is a rigid body said to be in equilibrium? State the necessary conditions for a body to be in equilibrium.
question_answer91) Define moment of inertia. On what factors does it depend?
question_answer92) How will you distinguish between a hard boiled egg and a raw egg by spinning it on a table top?
question_answer93) If two circular discs of the same mass and thickness are made from metals of different densities, which disc will have the larger moment of inertia about its central axis ? Explain.
question_answer94) Which one is easier to turn-a log or a bench of equal weight and length? The two have the same coefficient of friction with the ground. Explain.
question_answer95) The Moment of inertia of a disc about an axis passing through its centre and perpendicular to its plane is\[1/2M{{R}^{2}}\]. Derive the values of moment of inertia of the disc about its diameter and about an axis tangential to the disc lying on its plane?
question_answer96) What is the moment of inertia of a rod of mass M, length \[l\] about an axis perpendicular to it through one end? Given the moment of inertia about the centre of mass is \[\frac{1}{12}M{{l}^{2}}\]
question_answer97) What is the moment of inertia of a ring about a tangent to the circle of the ring?
question_answer98) What is the moment of inertia of a uniform circular disc of radius R and mass M about an axis passing through its centre and normal to the disc? The moment of inertia of the disc about any of its diameters is given to be\[\left( \mathbf{1}\text{ }/\text{ }\mathbf{4} \right)\text{ }\mathbf{M}{{\mathbf{R}}^{\mathbf{2}}}\].
question_answer99) The moment of inertia of a solid sphere about a tangent is \[\frac{5}{3}M{{R}^{2}}\], where M is mass and R is radius of the sphere. Find the M.I. of the sphere about its diameter.
question_answer100) The moment of inertia of a uniform circular disc about a tangent in its own plane is \[\frac{5}{4}M{{R}^{2}},\] where M is mass and R is the radius of the disc. Find its moment of inertia about an axis through its centre and perpendicular to its plane.
question_answer101) Using expressions for power and kinetic energy of rotational motion, derive the relation. \[\tau =I\alpha ,\], where letters have their usual meanings.
question_answer102) Explain if the ice on the polar caps of the earth melts, how will it affect the duration of the day?
question_answer103) 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 as heat, which one will win?
question_answer104) A uniform circular disc of radius R is rolling on a horizontal surface. Determine the tangential velocity (i) at the upper most point, (ii) at the centre of mass and (Hi) at the point of contact.
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