If net external force on a body is zero than

The correct answer is Option 2.

Key Points

• According to Newton's First Law of Motion, if no external force acts on a body, its acceleration is zero.
• This law is also known as the Law of Inertia, which states that an object will continue in its state of rest or uniform motion unless acted upon by an external force.
• The first law implies that in the absence of a net external force, the velocity of the object remains constant.
• Therefore, if the net external force on a body is zero, its acceleration must be zero, confirming that the body will either remain at rest or move with a constant velocity.

Additional Information

• Newton's Second Law of Motion:
  • This law states that the force acting on an object is equal to the mass of that object times its acceleration (F = ma).
  • It indicates that an object's acceleration is directly proportional to the net external force and inversely proportional to its mass.
• Newton's Third Law of Motion:
  • This law states that for every action, there is an equal and opposite reaction.
  • It means that forces always come in pairs; when one body exerts a force on another, the second body exerts an equal and opposite force on the first.
• Law of Inertia:
  • It is another name for Newton's First Law of Motion.
  • Inertia is the property of an object to resist changes in its state of motion.
  • Objects with greater mass have greater inertia and require more force to change their state of motion.
• Constant Velocity:
  • When an object's velocity is constant, it means the object is moving in a straight line at a constant speed.
  • In the absence of external forces, an object will continue to move with constant velocity according to Newton's First Law.