# Newton's First Law of Motion

• Newton’s First Law of Motion, also known as the Law of Inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
• This means that if an object is not moving, it will continue to stay still until a force makes it move. Similarly, if an object is already moving in a straight line at a constant speed, it will continue moving in this way unless a force changes its speed or direction.
• The term ‘inertia’ refers to the resistance of an object to changes in its state of motion. More inertia means the object is more resistant to changes in motion.
• A key concept to remember is that a stationary object has as much inertia as a moving object. The inertia is dependent only on the mass of the object, not its state of motion.
• This law applies to all objects, large and small, on earth and in space.
• Forces acting on an object can include gravity, friction, air resistance, or force applied by a person or another object.
• Real life situations reflect this law, such as the need to wear a seatbelt in a car. If the car suddenly stops, your body wants to keep moving due to inertia. The seatbelt applies a force to keep you from moving forward.
• An observation of Newton’s First Law is that it is easier to keep an object in motion once it starts moving, demonstrating the concept of inertia.
• The understanding of Newton’s First Law is vital for understanding and predicting how objects move when forces are applied or when forces are absent.
• Typical questions related to this law might require you to provide real-world examples, explain why certain events occur based on the law, or calculate force, mass, or acceleration given appropriate information. Be prepared for these types of problems in your revision.

It’s crucial to understand Newton’s First Law in-depth, as it’s foundational to subsequent concepts in physics. Aim to not just memorise the law, but understand it so that you can apply it to different situations and context-dependent problems.