If the force acting on the body is zero, then its momentum is -

The correct answer is constant.

Key Points

• When the force acting on a body is zero, according to Newton's First Law of Motion, the momentum of the body remains constant.
• This is because if no external force is applied, there is no change in the velocity of the body, meaning its momentum (which is the product of mass and velocity) stays unchanged.
• In the absence of force, an object at rest remains at rest, and an object in motion continues to move with constant velocity.
• Thus, the momentum is conserved and remains constant in the absence of an external force.

Additional Information

• Momentum:
  • Momentum is a vector quantity defined as the product of the mass and velocity of an object (p = mv).
  • It is conserved in an isolated system, meaning the total momentum before and after a collision remains the same if no external forces are acting on the system.
• Newton's First Law of Motion:
  • Newton's First Law states that a body at rest will stay at rest, and a body in motion will stay in motion unless acted upon by an external force.
  • This law is also referred to as the law of inertia.
• Implications of Zero Force:
  • Zero force means no acceleration, and thus the velocity of the object does not change.
  • In such a case, the object either remains at rest (if initially at rest) or continues to move with constant velocity (if initially moving).
• Momentum in Real-Life Applications:
  • Momentum is crucial in understanding collisions, such as car crashes, where the momentum before and after the collision helps in analyzing the impact forces.
  • It is also significant in the study of rocket propulsion, where the momentum change of exhaust gases propels the rocket forward.