question_answer

Directions for: The questions consist of two statements each, printed as assertion and reason. While answering these questions you are required to choose any one of the following five responses A. If both the Assertion and the Reason are true and the Reason is a correct explanation of the Assertion. B. If both the Assertion and the Reason are true but the Reason is not a correct explanation of Assertion. C. If the Assertion is true but the Reason is false. D. If both the Assertion and the Reason are false. E. If Assertion is false but Reason is true.

Assertion: A rocket moves forward by push" the surrounding air backwards. Reason: It derives the necessary thrust to move forward according to Newtons third Lav. motion.

A)  A        

B)                         B           

C)                         C                                           

D)  D            

E)  E

Correct Answer: A

Solution :

                The rocket consists of a combustion chamber in which liquid or solid fuel is burnt. The heat of combustion raises, the pressure very high inside the chamber. Therefore, hot gases (produced by combustion) are expelled from the tail of the rocket in the form of a jet with a very high exhaust velocity. Consequently the rocket rushes in the forward direction. The rocket exerts an action-force on the gas-je in the backward direction, while the gas-jet exerts a reactionary force on the rocket in the forward, applying the concept of Newtons third law of motion.