Luyện tập đồ thị năng lượng - thầy VNA

Today, Mr. Ngoc Anh will give you a lesson on the properties of energy in motion, and the picture that I give you here is the property of momentum according to density. As you know, with a parallel spring, momentum is chosen in a balanced position, its momentum is calculated in the formula as kx square divided by 2. The property of momentum according to density is a parabola with an ellipse on top, because it is kx square divided by 2. The parabola has an ellipse on top because k is a diameter, right? So this is just one type of property in many types of energy properties. In my science, I have built up to 90 episodes dedicated to energy, right? So this is just one type of property in many types of energy properties, right? And here I will give you a very light and very good lesson in the real life file in our group. As follows, a spring is parallel with a hardness of k equal to 75 N per meter. The property of momentum according to density is a parabola, and the property of momentum is chosen in a balanced position. The highest point on the axis is the property of momentum according to density, right? The total property of momentum according to density is 0.21 J. And people ask, what is the magnitude of momentum with the property of density? In E3, the magnitude is x0, right? If this x0 is a parabola, it must be a parabola, right? If x0 is a parabola, the drag force must be negative, because the drag force is F minus kx. But people ask, what is the magnitude of momentum with the property of density? k equals x, right? Your task is to find this x0. How much is k? 75 N. This is a fairly light and basic sentence in my 90-episode file. The more you go back and forth, there will be very terrible things. It's not easy like this, guys. Now, I will expand it. Let's do the calculation. E1 plus E2, right? Plus E3. Done? How much is k? 0.21 J, right? What is E1 in it? It is a function, right? OK? Let's continue. The ratio of x will have the ratio of momentum. Because our momentum is simply kx divided by 2. If x is multiplied by 3 times, how many times does our momentum multiply? 9 times, right? That is, E1 will multiply 9 times E3, right? Because of the equation of momentum, our E2 is kx divided by 2. Done? x is multiplied by 3 times, momentum is multiplied by 9 times, x is multiplied by 2 times, here it is multiplied by 2 times, but because of the equation of momentum, it is not important anymore. Got it? So how many times does momentum multiply? 4 times, right? So E1 multiplied by 9 times E3, E2 multiplied by 4 times E3. Calculate everything according to E3, guys. E1 replaced this number, is 9 times E3. Done? E2 replaced this number, 4 times E3, and this is just E3. Right? How much is k? 0.21 J. Done? 9 plus 4 plus 1 is how many? 14. Done? So we get E3, right? E3 is how many? Take 0.21 and divide by 14. Done? It is 0.015 J. 0.015 J. But what is the equation of momentum of E3? kx divided by 2. That is, kx divided by 2. Done? kx divided by 2. OK. We have k, instead of this, we get x0. We get x0. How much is it? Take answer multiplied by 2, divide by 7, 5. OK? Calculate one. It is 0.02 m. Very good. Very nice. 0.02 m. OK? And let it be m, no need to change it to cm, guys. Because when it comes to momentum, we still have to use the unit. m. Done? Finally, the equation of momentum of E3, the opposite magnitude, is k times the magnitude of x0. Got it? Because according to the momentum of E3, the magnitude is x0. Done? Change the equation. Take 75 times the answer. Done? It is 1.5 N. Right? 1.5 N. So what is the answer of our result? C. Right? The equation is C. Done? C. Done. Very easy and easy. And there are many more good questions. Things are more complicated, not just like this, guys. OK. Wait for you to learn with me. I will give you more good questions and more difficult questions. Like this. More. OK.