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.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
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.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
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.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
View Answer
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.