BCLN - Physics - Newton's First Law Introduction

A basic introduction to Newton's first law. It assumes that students have seen Forces videos 1-4 and are familiar with Fnet. http://www.BCLearningNetwork.com. 0:00at this point we've learned a lot about forces we've learned that forces on an 0:06object can be added to determine a net force and we can use that net for us to 0:12determine that changes in motion of the object and this isn't a simple concept 0:18in fact for most of human history people didn't understand this one of the first 0:26people to really begin deep thinking about why things move was aristotle 0:31aristotle was a Greek philosopher who lived in the 300 specie Aristotle came 0:38from a line of deep thinkers in Greece who came to explain the universe he was 0:44taught by Plato who is taught by Socrates all famous early philosophers 0:49Aristotle lived and worked in what we call the ancient world 0:55way back here in our historical timeline note that we are up here in the modern 1:03era now although aristotle was a brilliant luster much of his physics was 1:11incorrect 1:12given this it's worth exploring his ideas on forces and got it helps us to 1:18better appreciate how he convince people to think about forces his way and how we 1:25now have a much better understanding of the universe 1:31Aristotle talks that a force is required to keep an object moving ok it seems to 1:39make sense on the surface you give a push to start an object moving but the 1:45key word here to consider is keep a force is required to keep an object 1:52moving now people accepted aristotle's teaching in that it seemed to make sense 1:58for a lot of things that is if you're pushing on an object you stop pushing 2:04well the object eventually and generally stops in our day-to-day experience we 2:11don't see anything moving off forever but given that he didn't work well to 2:17explain why some things stopped more quickly than others and why things flew 2:24through the air and didn't stop when the forest stopped pushing it 2:28aristotle had to come up with all kinds of creative explanations for where these 2:35extra forces were coming from that kept these objects moving and it was a bit 2:41reaching but them it was the best explanation that people had to describe 2:47how things moved 2:50Isaac Newton was born in the sixteen hundreds right here in the early part of 2:56what we call the modern era so looking back at our timeline we see that newt 3:03who is influenced by others in the modern era including Copernicus and 3:07Galileo only change the way we look at forces after about two thousand years of 3:14people believing aristotle's work was the absolute truth despite all its 3:20difficulties all through the middle ages through most of recorded history 3:26progress was thwarted by quite an aerial view of motions and forces Isaac Newton 3:33suggested a brand new way of looking at motion and forces he laid out three laws 3:39that are the foundation of much of modern design Newton's laws have been 3:46the main tools which have accelerated technological progress in the modern era 3:51and got man to the moon 3:55well Aristotle but that forces kept things moving 3:59Newton explained that forces start things moving but that objects tend to 4:06keep moving on their own and less acted on by outside forces things don't 4:14naturally stop as Aristotle thought they naturally keep moving at the same speed 4:20and in the same direction this is Newton's first law and object will 4:27remain at rest or in uniform motion in a straight line unless acted on by an 4:35outside force basically it's saying that a first is required to change motion if 4:43there's no force than the object keeps moving along at the same speed in a 4:48straight line this relates to our net first in that if the net force is zero 4:55all the forces are balanced then the object's motion doesn't change 5:02weather continues to stay still or continues to move along at a high speed 5:07it just keeps doing what it's doing 5:13Newton explained that when a person is pushing an object and they suddenly stop 5:19pushing the object comes to a stop 5:23not because of any natural tendency but because of another force friction 5:29friction is acting in the opposite direction to your push all along but 5:35once you stop pushing it becomes the only force and that's why the object 5:42starts to slow down during the push our free body diagram looks like this and we 5:50calculate EFNet as 100 Newton's minus forty news for friction force and we get 5:5816 once we stop pushing the free body diagram changes the applied forces now