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A variable force, given by the 2-dimensional vector , acts on a particle. The force is in newton and is in metre. What is the change in the kinetic energy of the particle as it moves from the point with coordinates to ? (The coordinates are in meters)
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Important Questions on Work, Energy and Power
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A mass is attached to the end of a rod of length . The mass goes along a vertical circular path with the other end hinged at its centre. What should be the minimum velocity of the mass at the bottom of the circle so that the mass completes the circle?
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A stone is tied to a string of length and is whirled in a vertical circle with the other end of the string as the centre.At a certain instant of time, the stone is at its lowest position and has a speed .The magnitude of the change in velocity as it reaches a position where the string is horizontal ( being acceleration due to gravity)
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Assertion : No work is done by a force on an object when the point of application of the force does not move.
Reason : A small block of mass m is kept on a rough inclined surface of inclination a fixed in an elevator. The elevator goes up with a uniform velocity u and the block does not slide on the wedge. Then the work done by the force of friction on the block in time t will be
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Assertion : A spring has potential energy, when it is compressed (or stretched).
Reason : In compressing or stretching, work is done on the spring against the restoring force which is stored as potential energy.
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Assertion : Work done by the force or against the force does not depend on path, then force is called conservative force.
Reason : All central forces which follows the inverse square law are conservative forces
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Assertion : Potential energy is possible only in conservative force field.
Reason : Potential energy is a relative quantity but K.E. is an absolute quantity.
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Assertion : A body can have energy without having momentum.
Reason : A body can have momentum without having mechanical energy.
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Assertion : A truck and a car moving with the same kinetic energy are brought to rest by the application of breaks which provide equal retarding forces. Both come to rest in equal distance.
Reason : It is possible that the speed of a body is zero but velocity is not zero.
