Newton's First Law of Motion

CLAIMED BY VIVEKANAND RAJASEKAR (Fall 2016)

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 an unbalanced external force.

Also called the Law of Inertia, the law simply claims that there is a natural tendency of objects to keep on doing what they are doing.

A Mathematical Model

The first law states that if the Net Force acting on the object is zero, then there is no change in the velocity of the object. Velocity is a vector, which has both direction and magnitude, therefore if the Net Force is zero, neither the direction or magnitude can be changing.

This idea can be quantified in the following manner:

[math]\displaystyle{ \sum \mathbf{F} = 0\; \Leftrightarrow\; \frac{\mathrm{d} \mathbf{v} }{\mathrm{d}t} = 0. }[/math]

However, there are two particular instances of the object that this law could apply to.

1) The object is at rest and will stay at rest (Magnitude of velocity = 0) unless a nonzero force acts upon it.

2) The object is in motion (Velocity does not equal zero) and will continue to be in motion with the same velocity, proceeding in the same straight line unless a nonzero force acts upon it.

Examples

Simple

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.

See Also

Further reading or exploring

Science of NFL Football: https://www.youtube.com/watch?v=08BFCZJDn9w

Real world application of Newton's First Law: https://www.youtube.com/watch?v=8zsE3mpZ6Hw

Everything you want to know about Newton's First Law of Motion: http://swift.sonoma.edu/education/newton/newton_1/html/newton1.html

External links

NASA can help you understand: https://www.grc.nasa.gov/www/k-12/airplane/newton1g.html

References

https://thescienceclassroom.wikispaces.com/Newton's+First+Law+of+Motion

http://teachertech.rice.edu/Participants/louviere/Newton/law1.html

Matter and Interactions: Modern Mechanics. Volume One. 4th Edition.

Page Created by: Brittney Vidal November 10, 2015 <-- For Credit Page Edited by: Vivekanand Rajasekar November 27, 2015 <-- For Credit

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