Trouble with definition of Newton's First Law

In summary, the lecturer in the dynamics class defined Newton's First Law as the existence of an inertial frame where an object with mass m moves in a straight line with constant velocity and experiences no net force. This may seem contradictory to the concept of inertial frames not being able to accelerate, but in the context of objects falling or accelerating on Earth, the frame of reference can keep up and still be considered inertial.
  • #1
Rwindsor1
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The lecturer in my dynamics class defined Newton's First Law to be 'There exists at least one inertial frame with respect to which mass m moves in a straight line with a constant velocity. In this frame no net force acts on m.'

This has confused me; I thought inertial frames could not accelerate? Therefore how can this be true if mass m is accelerating? How can the frame 'keep up'?
 
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  • #2
What was the full context of the discussion. Was he referring to objects falling/acelerating on the Earth?

If you fall with the object then to someone on the Earth you and object would be accelerating. However, relative to you, you and the object are in an inertial frame of reference.

http://en.wikipedia.org/wiki/Inertial_frame_of_reference
 
  • #3
Ah I see, thanks for clearing that up :)
 

1. What is Newton's First Law?

Newton's First Law, also known as the Law of Inertia, states that an object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an external force.

2. Why is it referred to as the "Law of Inertia"?

The term "inertia" refers to an object's resistance to change in its state of motion. This law describes how objects will maintain their current state of motion unless acted upon by an external force, which is known as inertia.

3. How is this law relevant to everyday life?

This law is relevant in many everyday situations, such as why objects stay in place if not moved or why objects continue to move in a straight line unless something stops them. It also explains why seatbelts are necessary in a car to keep passengers from moving forward when the car suddenly stops.

4. What are some common misconceptions about Newton's First Law?

One common misconception is that this law only applies to objects at rest, when in fact it also applies to objects in motion. Another misconception is that this law only applies to objects on Earth, when in fact it applies to all objects in the universe.

5. How did Newton's First Law contribute to the development of modern physics?

Newton's First Law, along with his other laws of motion, laid the foundation for the study of mechanics and the understanding of how objects move. It also led to the development of the concept of inertia, which is a fundamental principle in physics. This law is still widely used and referenced in modern physics and engineering.

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