[Music] have you ever experienced riding a car and then the car exhilarates abruptly making you feel as if your body is pulled to the back or when the driver suddenly steps on the brakes and you feel the seat belt tighten that's the work of newton's first law of motion the law of inertia it explains how an object responds to changes in motion but before anything else let's talk about force and motion force is any push or pull that causes changes in the motion of an object there are two types of force contact force and non-contact force contact force is present when two or more services or media touch and interact a specific type of contact force is friction the object's resistance to motion on the other hand non-contact force is constantly present in nature and does not need human intervention to arise take for example the sun and planets they exert a gravitational pull on each other despite their large spatial separation so even when your feet leave the earth and you are no longer in physical contact with the earth there is a gravitational pull between you and the earth now let's talk about motion motion is caused by unbalanced forces and can be described with the following aspects speed velocity and acceleration speed is the length of distance traveled in a certain amount of time while velocity is the rate of change of displacement of an object and acceleration is the rate of change of velocity of an object sounds confusing let me give you an example this car is going 100 miles per hour this is speed because it is only telling how fast the car is going this car is going 100 miles per hour east this is velocity because it is telling the speed and direction the car is going the car slowed down at the stop sign then sped up this is acceleration because the car changed its speed now that we already know the fundamental concepts of force and motion we can now understand newton's laws of motion the response of an object to changes in motion can be explained by isaac newton's first law of motion the first part of newton's first law of motion stated that an object at rest will remain at rest unless acted on by an unbalanced force for example a ball at rest will remain at rest unless it is kicked the second part of newton's first law of motion stated that an object in motion continues to move with the same velocity unless acted on by an imbalanced force this rolling ball will remain in motion when there is no friction or force stopping it the property that resists the changes in an object is called inertia inertia is an inherent property of an object to resist change it is independent from external force and it is mass dependent meaning massive objects have greater inertia while smaller objects have lesser inertia let us consider an example of an object address the box is acted upon by normal force and gravitational force these forces balance each other and no other force is acting on the box thus the box remains at rest let us look into examples of external forces imagine a spacecraft in space when the engines are turned off a spacecraft in space will move with constant speed in the same direction however when the spacecraft's engine is turned on the spacecraft will now experience an unbalanced force this force will change the speed and direction of the spacecraft remember my first example imagine you are riding a car and the car experiences a sudden stop inertia will keep you from moving along with the car you will stop moving when you hit another object such as the steering wheel or the windows but this will cause you severe injury seat belts prevent this from happening since it acts as an external force preventing you from moving along with the car let's have a short activity so we can apply what we just learned get a coin a glass and a piece of cardboard procedure arrange the setup as shown slowly pull the cardboard with your hand and observe what happens arrange the setup again as shown this time quickly flick the cardboard with your finger observe again what happens what did you notice what happened to the coin when you slowly pulled the cardboard how about when you quickly flick the cardboard now remember an object press will remain at rest and an object in motion will remain in motion unless acted on by an imbalance force this behavior of how a body changes in motion can be demonstrated by newton's law of inertia or the first law of motion that's it for now see you in our next video and don't forget to keep your minds busy thanks for watching our video if you want to see more content from the learning bees please hit the subscribe button see you later