in this video I'll talk about the average breaking force most of you drive a car when you drive a car and then you see a stop signal what I do you apply the weight now the question is how long does it take to stop the car or how much force you applied that's exactly the problem we're going to do in this video so here we have a car and the mass of the car is 1500 kilogram that's the mass of the car and the car is moving at 30 meter per second in a straight line okay and then the driver applies the brake and the car comes to stop in 550 meter at this point now the car is in complete rest right and the distance it has moved is 550 meter before it comes to a complete stop know you have to find out how long does it take to stop the car and what is the average braking force or how much average force you applied to a stop the car okay so so let me write down all the the given values so the velocity which the initial velocity is 30 meter per second the mass of the car is 1500 kilogram the s is the distance which is 550 meter and the V is the final velocity this is the final velocity and the final velocity at this point is zero why because the car has to come to a complete stop so this velocity zero now let's calculate the time I think I haven't calculated the time but I will calculate this in we have firstly a calculator the acceleration here but let's calculate the acceleration first so the kinematic equation that I'm going to huge is V squared is equal to u square plus - where's let me erase this one first okay so here we're finding out the acceleration first so V squared oops the V squared is equal to u square plus where's dusty a standard kinetic equation the V is the final velocity which is zero because a car is at complete rest and U is the initial velocity which is 30 meter per second to a we do not know the acceleration so we're going to figure it out and s is the distance travel the distance traveled is 550 liter so this is what it is now and if we saw a you'll get the negative 0.82 meter per second square what is the negative mean here the negative means if it took me any point here at any point the let's say here the car at any point the velocity is in this direction and the acceleration is in the opposite direction the velocity the velocity and the excavation at any point it's in opposite direction because the car is coming or to stop or the velocity is decreasing that's what this negative sign means the negative sign means the velocity or the acceleration is opposite to the velocity or in other words the velocity is decreasing it is coming to a stop okay so once we know the acceleration then it is fairly simple to use the average Britain force just by Newton's second law of motion the force is equal to mass times acceleration the mass is 1500 and it just calculated the acceleration which is 0.8 - the magnitude and simplifying it will give you the 230 Newton and again the negative sign the negative sign he admits the force is opposite this force is opposite it that's how you come to stop some some has something has to keep you dragging to make you stop if you moving so that's what the negative sign means now let's find out the the time now we have a home to calculate the time here so it is going to calculate the time here the time it takes to the time to come to a stop so again we're going to use a kinematic equation which is this time let's see I'm going to use V equals to u plus 80 what is the V again you know that the V is the final velocity and what is the final velocity the final velocity is zero and what is the U U is the initial velocity and what is that thirty meter per second nice plus a what is the acceleration we just calculated which is negative point eight two so this is negative point eight two and the time we need to find it out and if we saw the time let's use the calculator and solid so it has to be thirty divided by 0.8 two and here it will be positive because if you take the negative to the other side it will be positive so 30 divided by 0.8 to this is 36.6 second 36.6 second that's the time it takes to completely stop okay or you can also find out you can use this equation to there are lots of equation you can use I'm writing down here as it goes to UT plus half ay T Square even if you use this equation you should be able to get it but this is a quadratic equation then you have to solve the quadratic equation so this is the simplest equation okay so that's it it's a pretty straightforward thing to do again if you have any questions write down your questions in the comment section below and at the end do not forget to Like share and subscribe the channel thank you very much