Newton's First Law of Motion

This topic covers Newton's First Law of Motion

The Main Idea

Newton's First law states that an object at rest will stay at rest and an object in motion will stay in motion with the same speed and direction unless acted upon by unbalanced force.

This is also known as the "Law of Inertia"

A Mathematical Model

The quantification of this law is done by quantifying the amount of interaction, or the Force. For an object to have uniform motion it can either have zero forces acting on it or the forces may cancel each other out. If there is a force acting on an object to the right, and a simultaneous and equal magnitude force acting on it to the left, then the object will have uniform motion. This means the object will stay in motion with the same speed and direction. But, if there is an unbalanced force acting on an object, then the speed and/or direction of the object will change.

Examples

Let's do some examples and critical thinking similar to the book:

Question 1: In order to move a box with constant speed and direction across a table what do you have to do?

Answer: You would have to push the box the entire time across the table. With the same magnitude and direction of course. But why doesn't it just keep on moving after one push you ask? Well the net force on the box must equal zero for the box to continue moving at the same speed and in the same direction. So with the outside forces acting on the object, you would have to keep pushing to cancel them out and keep the motion of the object constant.

Question 2: Is a change in position an indicator of interaction?

Answer: Sometimes yes and sometimes no. It depends. If the change in position is a result of constant speed and direction of an object then no, it is not an indicator of an unbalanced force. Further data (like velocity at each position) would be needed to decide if an object is experiencing an interaction from an outside force.

Connectedness

This topic is connected to every aspect of life. Every time you get in a car or drop something on the floor or trip over a rock Newton's First Law is demonstrating itself to you. The connections of this topic to the real world is an endless list of possibilities.

History

This theory was originally discovered by Galileo who conducted experiments on the concepts of inertia and acceleration due to gravity. Galileo studied the movement of balls on smooth and rough surfaces, developing the idea of friction. Isaac Newton further studied these concepts and ideas and presented his 3 Laws of Motion. The first of these 3 laws, as we know, stated that an object in motion will stay in motion with the same speed and direction until an unbalanced force acts on it. And with the absence of friction or other forces, an object will continue moving forever.