A car accelerates on a horizontal road due to the force exerted by
Friction force applied by road on the car act in the direction of the motion which is responsible to move the car.
If a fly collides with the wind shield of a fast moving bus which experiences an impact force with a larger magnitude :
From Newton's third law of motion both bus and fly will experience equal force in opposite direction.
If action force is gravitational force, then reaction force :
Action and Reaction forces are of same nature.
Assertion (A): According to Newton’s third law of motion, action and reaction forces are equal in magnitude and opposite in direction.
Reason (R): Net force on a body due to action-reaction pair is always equal to zero.
Assertion (A) is true: Newton's third law states that action and reaction forces are always equal in \(magnitude\) and opposite in \(direction\).nReason (R) is false: Action and reaction forces act on *different* bodies, so they cannot cancel each other out to produce a net force of \(0\) on a *single* body. Therefore, (A) is true but (R) is false.
Assertion (A): When two particles interact, net force on either particle is zero.
Reason (R): Both experience action and reaction which are equal and opposite.
Assertion (A) is false: When two particles interact, they exert forces on each other. Unless these interaction forces are exactly balanced by other external forces, the net force on *either* particle will generally *not* be zero, causing them to accelerate. Only the net force on the *system* of two interacting particles is zero (if no external forces are present).
Reason (R) is true: According to Newton's third law, when two particles interact, they exert action and reaction forces on each other which are always equal in magnitude and opposite in direction. Given that (A) is false and (R) is true, and option 'A is false but R is true' is not explicitly provided, option (4)
'Both (A) and (R) are false' is selected as it correctly identifies (A) as false.
Assertion (A): A man standing at rest on ground. Force exerted by man on ground is equal to weight of man.
Reason (R): Earth attracts man by force \(mg\) hence by Newton’s third law, man also attracts earth by same force.
Assertion (A) is true: the man exerts a force equal to his weight on the ground. Reason (R) is true by Newton's third law of gravitation for action-reaction. However, Reason (R) explains gravitational forces, not the contact force on the ground, so it is not a correct explanation for (A).
Assertion (A): A block is hanging from spring. Spring force on block and gravitational force on block are not action and reaction pair.
Reason (R): Action and reaction force acts in opposite direction.
Action and reaction pairs act on different bodies. Both spring force and gravitational force act on the same block, so they are not an action-reaction pair. Both A and R are true statements, but R does not correctly explain A.
Assertion (A): According to the Newton’s third law of motion, the magnitude of the action and reaction force in an action reaction pair is same only in an inertial frame of reference.
Reason (R): Newton’s laws of motion are applicable only in inertial reference frame.
Newton's third law of motion (action-reaction pairs) is universally valid, not only in inertial frames. Thus, A is false. While Newton's first and second laws require inertial frames, the third law is more fundamental and applies in all frames. Thus, R is also false.
Assertion (A): A rocket moves forward by pushing the surrounding air backward.
Reason (R): There is an equal and opposite reaction to every action.
Assertion (A) is false; rockets achieve propulsion by expelling hot gases backward, not by pushing the surrounding air. They work in vacuum. Reason (R) is true, stating Newton's third law. Thus, (A) is false and (R) is true. Option (4) is selected as it correctly identifies (A) as false.
Assertion (A): An air tight cage in which a bird is sitting, is suspended from a spring balance. If the bird starts flying upwards with some acceleration, then the reading of the balance will increase.
Reason (R): The weighing machine measures the actual weight of a body.
When the bird flies up with acceleration, it pushes more air downwards, increasing the effective weight measured. So (A) is true. A weighing machine measures apparent weight, not always actual weight. Thus (R) is false.