Question

Assertion: A Helicopter must necessarily have two propellers.

Reason: Two propellers are provided in a helicopter in order to conserve Linear Momentum.

• A. Both assertion and reason are true.
• B. Both assertion and reason are false.
• C. Assertion is true and reason is false.
• D. Assertion is true and reason is true.

Answer 1

The correct option is C

Assertion is true and reason is false.

The explanation for assertion:

1. Angular momentum is the property of a rotating object obtained by multiplying the inertia of the object and the angular velocity of the object.
2. Linear momentum is the property of any moving object obtained by multiplying the mass and velocity of the object.
3. Now let's consider the helicopter the main propeller which is on top creates some angular momentum.
4. The helicopter has to counter that momentum in some way otherwise it will spin itself to balance that momentum.
5. The second propeller which is at the back creates a counter momentum so that helicopter remains stable.

The explanation for the reason:

1. There exist two propellers in the helicopter to balance the angular momentum but not linear momentum.

Hence, the correct answer is option C.