[Music] hi and welcome back to free science lessons. co.uk by the end of this video you should be able to describe Newton's first law of motion you should then be able to apply Newton's first law to moving and stationary objects now Newton's Laws of Motion describe the effects that forces have on the motion of an object there are three laws of motion and we're going to be looking at them in the next few videos I'm showing you Newton's first law of motion here if the resultant force acting on a stationary object is zero then the object will remain stationary if the resultant force acting on a moving object is zero then the object will continue moving in the same direction at the same speed in other words with the same velocity now this looks a bit tricky but I promise you it's easier than it looks I'm showing you here a stationary object with no forces acting on it because there's no resultant Force the object will remain stationary this shows a stationary object with a 50 Newton force acting to the right and also a 50 Newton force acting to the left in this case the forces are balanced and the resultant force is zero so once again this object will remain stationary okay now this shows an object that's moving there are no no forces at all acting on this object so because there's no resultant Force both the speed and the direction of this object will stay the same in other words the object will continue to move with the same velocity this shows another object that's moving in this case there's a 50 newon force acting to the right and a 50 Newt force acting to the left because the forces are balanced the resultant force is zero so once again both the speed and direction of this object will stay the same the object will continue to move at the same velocity so the key fact is that the velocity of an object will only change if a resultant force is acting on the object I'm showing you here a car driving at a constant speed of 15 m/s the driving force of the engine is acting to the left because the car is moving at a constant speed there must be an equal force acting to the right scientists call these the resistive forces the resistive forces include friction with the air and also friction with the road okay so let's look now what happens when a resultant Force acts on an object this shows a stationary object we're applying a resultant force of 50 Newtons acting to the right this resultant force causes the object to accelerate to the right in other words a resultant force causes an object speed to change this shows an object moving at a constant speed where applying a resultant force of 50 Newtons acting to the left in this case the resultant force causes the object to decelerate in other words slow down so once again we can see that a resultant force causes an object's speed to change a resultant force can also change an object's Direction I'm showing you here an object moving with a constant speed a resultant force is acting on the bottom of the object this causes the object to accelerate upwards remember you'll find plenty of questions on new first law in my vision workbook and you can get that by clicking on the link above [Music]