State Newton's first law of motion.

Newton's first law of motion states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.

This law is also known as the law of inertia. Inertia is the tendency of an object to resist changes in its motion. An object at rest will remain at rest, and an object in motion will continue to move at a constant velocity in a straight line, unless acted upon by an external force.

The first law of motion can be mathematically expressed as F = ma, where F is the net force acting on an object, m is the mass of the object, and a is the acceleration of the object. If the net force acting on an object is zero, then the acceleration of the object is also zero, and the object will remain at rest or in uniform motion in a straight line.

This law has many practical applications, such as in the design of seat belts and airbags in cars. In a car crash, the passengers tend to continue moving forward at the same speed as the car before the crash. The seat belt and airbag provide an external force that slows down the passengers and reduces the risk of injury.

In conclusion, Newton's first law of motion is a fundamental principle of physics that describes the behavior of objects at rest or in motion. It is important to understand this law in order to understand the behavior of objects in the world around us.