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Answer» (A) Real and pseudo forces, | No | Real force | Pseudo Force | | i | A force which is produced due to interaction between the objects is called real force. | A pseudo force is one which arises due to the acceleration of the observer’s frame of reference. | | ii | Real forces obey Newton’s laws of motion. | Pseudo forces do not obey Newton’s laws of motion. | | iii | Real forces are one of the four fundamental forces. | Pseudo forces are not among any of the four fundamental forces. | | Example: The earth revolves around the sun in circular path due to gravitational force of attraction between the sun and the earth. | Example: Bus is moving with an acceleration (a) on a straight road in forward direction, a person of mass ‘m’ experiences a backward pseudo force of magnitude ‘ma’. |
(B) Conservative and non-conservative forces, | No | Conservative | Non-conservative forces | | i | If work done by or against a force is independent’ of the actual path, the force is said to be a conservative force. | If work done by or against a force is dependent of the actual path, the force is said to be a non-conservative force. | | ii | During work done by a conservative force, the mechanical energy is conserved. | During work done by a non‐ conservative force, the mechanical energy may not be conserved. | | iii | Work done is completely recoverable. | Work done is not recoverable. | | Example: gravitational force, magnetic force etc. | Example: Frictional force, air drag etc. |
(C) Contact and non-contact forces, | No | Contact forces | Non-contact forces | | i | The forces experienced by a body due to physical contact are called contact forces. | The forces experienced by a body without any physical contact are called non-contact forces. | | ii | Example: gravitational force, electrostatic force, magnetostatic force etc. | Example: Frictional force, force exerted due to collision, normal reaction etc. |
(D) Inertial and non-inertial frames of reference. | No. | Inertial frame of reference | Non-inertial frame of reference | | i | The body moves with a constant velocity (can be zero). | The body moves with variable velocity. | | ii | Newton’s laws are | Newton’s laws are | | iii | The body does not accelerate. | The body undergoes acceleration. | | iv | In this frame, force acting on a body is a real force. | The acceleration of the frame gives rise to a pseudo force. | | Example: A rocket in inter-galactic space (gravity free space between galaxies) with all its engine shut. | Example: If a car just starts its motion from rest, then during the time of acceleration the car will be in a non- inertial frame of reference. |
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