Physics – Newton’s Second Law of Motion

Do you remember the Newton’s first law of motion? It says that an object will continue to do what it’s doing unless acted upon by an unbalanced force or some net force! Now the important question is what happens when there is net force acting on an object? That’s precisely what the second law of motion will discuss. Do you remember understanding the first law of motion with a simple diagram? If the forces are balanced the acceleration will be zero. In the first case, the object will continue to remain at rest. And in the second, the object will continue to stay in motion at the same velocity and in the same direction. Don’t forget. These two cases will remain true only if the forces are balanced. Only if the net force is zero. Now let’s try to create a similar diagram for the second case. If the forces are unbalanced, then there will be acceleration. We saw that in the previous video. And now we come to the interesting part! Let me ask you a question, and I’m sure you can answer it. On which two factors do you think the acceleration will depend on? I want you to tax your brain a bit. Let me repeat my question. On which two factors do you think will the acceleration depend on? Okay, let’s say there is an object on a table. You apply a net force of 10 units on it. And then you apply a net force of 20 units on it . In which case do you think the acceleration will be more? Of course the one in which the force was more. So we can say that one of the things the acceleration depends on is net force. If it’s more, then more will be the acceleration. If it’s less then lesser will be the acceleration. Acceleration depends directly on the net force. Come on, now i want you to think about the second quantity the acceleration will depend on. Let’s say there are two objects on the table. One has a mass of three kilograms, and the other has a mass of five kilograms. Now if you apply net force of ten units to each of them, which one do you think will accelerate more? Surely, it’s the three Kg one because it has lesser mass. Lesser the mass more the acceleration. And more the mass lesser the acceleration. Hence we can say, that acceleration depends inversely on the object’s mass. If you understand this concept well then understanding the second law of motion will be very easy. Mathematically, it can be written like this. In simple terms, the acceleration is directly proportional to the net force applied, and inversely proportional to the mass of the object. That’s the second law. Or as more people understand it like this. The net Force is the product of Mass and acceleration. With this can you tell me the units of force? That should be easy. The standard unit of mass is kilograms. And that of acceleration is meters per second squared. So the unit of force is, kilograms times meters per second squared. And this is what we call as Newton. One Newton is one kilogram times meters per second squared. So if the mass of the object is ten kilograms, and the acceleration is 10 meters per second squared, then the force will equal 100 Newtons. We can say that one Newton is defined as the amount of force required, to give a 1 kilogram mass and acceleration of 1 meter per second Squared.

100 Replies to “Physics – Newton’s Second Law of Motion

  1. Again… You made a mistake when you said that an unbalanced force leads to an object being able to move without specifying that it wouldn't move in the same direction of the balanced force (balanced forces restrict motion at the area they act on)… You can not maintain the same velocity as you fall towards the ground because you are bound to accelarate the more you aproach the ground because the ground is pulling you closer like a magnet… so when you said in the last video that the astronant can maintain the same velocity because of the balance of air pressure as opossed to the gravitational pull, you forgot that ''g'' stands for acelaration due to gravity meaning its not possible to fall at a balanced speed unless there is no constant gravitational pull acelarating you down nor air pressure slowing your fall down… And also, there needs to be an ''unbalanced force'' acting in an instance to move you from A to B and the only way you can continue to move with the same velocity is if there are no forces present to counter the motion from A to B…. So, the movement of can only occur if there are no balanced forces between A and B cuz they will cancel out leaving the object at rest.

  2. Thank you so much…😊
    This concept was very hard to understand but you minimized it in a 4 minute video… Its magic.
    And ofcourse i have understanded it as well…
    Very good keep it up.

  3. Give complex exercises at the end of the video so that students can try it and make a related video on solutions and explanations.Btw , good work! Extra points for keeping the videos brief and to the point 👍

  4. No object is put on
    motion without the hit of an external force. Since there should be an
    initially force applied to an object in order for the object to start
    it state of motion, therefore there is acceleration involved for any
    object in motion. As long as the acceleration is not zero the object
    velocity should increase and increase to infinity, assuming the
    object is not under the influence of any external forces at all.

    Example, suppose an

    object is suspended without any, whatsoever, forces acting on it.
    Now, you hit the object with something. So the object will start its
    motion. This means the object will begin with acceleration. Does
    this positive acceleration remains with the object. Again assuming
    the object not being subjected to any external forces. If the object
    is under the influence of acceleration due to the initial hitting
    then the velocity of the object will keep increasing and increasing.
    So an object in motion will not continue its journey with constant
    velocity. That is an object in heaven in motion must be under a
    positive acceleration and with a non zero acceleration the velocity
    keep increasing. Would you please clear me about this subject? Thank

  5. I really love your videos!!..
    They will help me a Lott to prepare for my exams…as I'm studying 6th class we have the lessons 1.kinematics and 2.dynamics…they are very difficult for me to understand..butt,,after watching your videos..I have been understood very easily..😳😳😎😎😎😳😳😳😎😎

  6. at 3:11 you said, "can you tell me the units of force" which is N. however then you said "the standard unit of MASS is kg" ? im confused?

  7. I'm an student studying in Tamilnadu stateboard. When I was doing my 9 Th standard your videos helped me a lot. Thanks for uploading the videos (not this one alone but all)


  9. on your video says 1 N to 1Kg/m2. It is wrong 1N = .981Kg/m2 Many of them are actually following it. Be more cautious on what your putting here

  10. Newton's Second Law of Motion needs a slight correction since they did not know about cubing a number in Newton's era we can assume that this may have been overlooked. As such F=ma^2 is a natural correction that can be easily proofed through calculation, formulation, and experimentation. This correction is 33% more accurate if you do not accept it proof it yourself.

  11. What happens when the object is moving at a constant velocity and hit's another object that is stationery? how do i calculate the force of the impact?

  12. Thermodynamics principle is misconception. Perpetual Motion Machine is possible. See bellow
    The WORK OUTPUT is more than double the WORK INPUT.

    A 15 ball billiard pool to be strike by white mother ball
    When I computed the work done in pool (billiard) the white mother ball break the 15ball.

    F = 30lbs (White Mother Ball); D = 3ft (Distance from the white mother ball to the first ball to strike)
    W = F X D; W = Work; F = Force; D = Distance

    W = F X D;  W = 30lbs  x  3ft  =  90Ft.lbs      

    First two ball extreme corner of the billiard ball 2 out of 15 ball
    W = F X D; W = 30lbs x 3ft = 90ft.lbs  X  2ball = 180 ft. lbs

    The remaining ball (13pcs ball) can produce more than 90 ft.lbs
    The computation shows that the output work done is higher than the input work done. That principle can make free energy machine

    Appreciated for your reply

    Thank you.

    Abel Urbina
    Abel Urbina Free Energy  Super Machine

  13. I thought physics is so hard and I hated it but by this video it looked so simple and easy and I loved it
    Thank you so much!

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