What is Newton's first law of motion?

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

This law, also known as the law of inertia, is fundamental to our understanding of motion. It essentially tells us that if no net force is acting on an object, then the object will maintain its current state of motion. This could be either at rest or moving in a straight line at a constant speed. The 'net force' is the vector sum of all the forces acting on the object. If this net force is zero, then there is no change in the motion of the object.

The concept of 'inertia' is key to this law. Inertia is the property of an object that resists changes in its state of motion. The more mass an object has, the more inertia it has, and the more force it takes to change its motion. This is why it's harder to push a heavy car than a bicycle.

This law also implies that motion is relative. If you're in a car moving at a constant speed, you don't feel any force acting on you. You can throw a ball up in the air and it will come straight back down, just as it would if the car was at rest. This is because there is no net force acting on you or the ball.

Newton's first law of motion is a cornerstone of classical physics. It helps us understand the relationship between forces and motion, and it lays the groundwork for the other two laws of motion. It's a simple yet powerful law that governs the motion of objects in our everyday lives and in the universe at large.