Question

Assertion :A rocket work on the principle of linear momentum. Reason: Whenever there is the change in momentum of one body, the same change occur in the momentum of the second body of the same system but in the opposite direction.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Yes definitely rocket works on principle of linear momentum. Assertion is correct.

But reason is correct as because when the rocket engine fires it pushes fuel out of the end of the rocket. Suddenly part of the fuel has momentum mv towards left.

Since the total momentum of the system was zero before the rocket fired it must still be zero. This means that the rocket must have an equal momentum to the right.

$\Rightarrow P_{rocket}=-P_{fuel}$

The negative sign means that the two momentum vectors are in opposite directions (and therefore cancel ). Ever though the momentum of the rocket and their velocities are not of same size. As the two momentum vector are in opposite direction we conclude that whenever there is the change in momentum of one body the same change occur in the momentum of the second body of the same system in the opposite direction so rocket get, fired and it blows up.

Hence, both assertion and reason are correct and reason is the correct explanation for assertion.