hi guys in this lesson we're going to be talking about newton's first law now trust me it is super easy just pay attention so i want you to really visualize this close your eyes if you have to imagine you are busy cycling on a flat flat road and you're trying to keep your speed at let's say 20 kilometers per hour if you don't pedal what will happen to your speed well you will slow down if you pedal too quickly then your speed will increase so what would you have to do to keep your speed at
20 well your your your pedaling would have to be in a specific way so so your peddling mustn't be too slow and it mustn't be too fast what is it that's trying to slow you down well remember in in high school we don't look at air resistance so that's not something we're going to look at it's the friction on the road between the road and your tires okay that's trying to slow you down and what's trying to speed you up well that's the force of you on the pedals so if you want to keep your
bike going at 20 kilometers per hour those two forces must be completely balanced if the pedals become more than the friction then you will start to speed up then your speed's going to start going 22 23 24 and so on if you stop pedaling then it's only friction acting on you and now all of a sudden your speed is going to start slowing down so it's going to go 18 17 16 and so on but if you want to keep your speed at 20 kilometers per hour your forward forces must be the same as your
backwards forces that is what newton's first law is all about now the next part i want to talk about is let's say we've got this object hanging from the ceiling okay so this is the ceiling and then here we've got some object now let's say it's just hanging there that means it's not moving that means that all the forces acting on that object are balanced now what forces are acting on that object well there's gravity that's trying to make it go down but then there's the tension in this rope and so we'll call that ft
that's something we haven't looked at yet f t for tension and f g for gravity if those two forces are balanced then the object won't move so we can now summarize newton's first law but remember i'm summarizing it in my own words you need to use the definition that your teacher's giving you and so here it is guys now remember my definition is very close to the normal definitions i just like to phrase it in a way that is easy to understand so it says that an object will remain at rest so remember this object
is at rest or it will continue to move at a constant velocity like this car on his bicycle unless the forces are unbalanced so if the pedals or if the force of the person suddenly becomes more than the friction then the person will start accelerating they won't move at a constant velocity if we put a heavier object over here and let's say that this rope cannot stretch any further then the rope will snap and the object will start accelerating so let me read it again an object will remain at rest such as this one or
will continue to move at a constant velocity velocity is like speed and if it's constant remember 20 kilometers per hour unless the forces are unbalanced and so that's all i want to talk about in this lesson newton's first law and so thank you for watching
