Question

A jet engine works on the principle of:

• A. Conservation of linear momentum
• B. Conservation of kinetic energy
• C. Conservation of angular momentum
• D. Conservation of inertia

Answer 1

The correct option is A

Conservation of linear momentum

Correct Option: Option A

1. Linear momentum $\left(p\right)$ of a body is the product of its mass and velocity, $p=mv$.
2. The law of conservation of linear momentum states that, “A body in motion does not change its total momentum until an external force is applied on it”. That can be mathematically expressed as, $Initialmomentum=Finalmomentum$.
3. When the fuel in a jet engine is combusted, it produces a high volume of gases in the backward direction which attains large momentum due to high velocity.
4. Due to this an equal and opposite momentum is gained by the jet engine allowing it to move in the forward direction with a high velocity.
5. Thus, a jet engine works on the law of conservation of linear momentum.

Incorrect options:

Option B

1. The law of conservation of energy states that “The total energy of a system remains the same.”
2. The jet engine imparts an equal and opposite momentum to the jet engine after releasing of gas.
3. With this momentum, it moves forward with greater speed.
5. The jet engine does not work under the Conservation of kinetic energy
6. So, option B is incorrect.

Option C

1. The law of conservation of angular momentum states that “A body in rotational motion retains its total momentum until an external torque is applied to it”.
2. There is no rotational movement present in a jet engine.
3. Hence the jet engine does not work under Conservation of angular momentum
4. So option C is incorrect.

Option D

1. Inertia can be described as the ratio of angular momentum and angular velocity.
2. The conservation of inertia says that a rotating rigid body maintains its state of uniform rotational motion until and unless any force is applied.
3. Hence the jet engine does not work on conservation of inertia.
4. So, option D is incorrect.

Hence, option A is correct.