What is Force?

Professor Mac is standing in front of a broken wall lying on the ground with the words "Professor Mac Explains Force" in large yellow text in the background.


My video explaining force is now available. In it I explain the concept of force and the effect forces have on objects through a series of high quality animated experiments. Force is a concept used in physics and engineering and you may think of it as a push or a pull. 


Professor Mac is standing in front of a block of wood on a table and is pushing it forward to illustrate force


Force has a magnitude (strength) and a direction. If we apply a force to an object, pulling it to the left, the object will accelerate to the left. If we apply a force to an object, pulling it to the right, the object will accelerate to the right. Therefore you can see that the direction of a force is important, as the effect it has on an object will be different depending on its direction.

Since a force has magnitude and direction, it is referred to as a vector in mathematical calculation. Therefore when analysing forces we use arrows to represent the magnitude and direction of the force.


A rocket is shown high above the sand coloured ground during launch, with yellow, blue and green arrows illustrating the forces acting on the rocket


We use the newton as the unit of measurement of the size of a force. To get a feel for the size of a newton, hold an averaged sized apple in your hand. The vertical force you feel is due to the weight of the apple and is approximately equal to a force of one newton. 


Professor Mac is holding an apple, with a vertically down arrow, showing the force due to the apple weight is approximately one newton


Newton’s laws of motion use force to explain the motion of an object. If you know the force applied to an object you can predict the object’s acceleration.

In structural mechanics we can use force to predict the deformation of an object. If the force applied to an object exceeds the object’s strength, there will be failure of the object. In my video, I illustrate this with reference to a poorly constructed wall. When I push on the wall with a force greater than the strength of the wall, the wall fails at its foundation, resulting in the wall collapsing to the ground.

So here is my video. It is a fast paced summary of force and I hope you enjoy it.




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14 Responses

  1. Trisha says:

    Great I love your work!!

  2. abhinavsolankey says:

    Very good effort to express the fundamental concepts of physics to solve the how ,when and why.thanks professor mac

  3. hardiv says:

    your videos help alot! keep up the good work!

  4. hardiv says:

    Hello proffessor! you videos are great1 keep up the work! 🙂 (i have learnt alot!)

  5. Eddie Clarke says:

    Thank you for this clear and entertaining presentation. Physics is the only exam I ever failed, and it has bugged me ever since, so I hope to make some progress this time round 😉 I guess a force is anything that tends to change the acceleration of a body. Alternatively, if the acceleration of something changes, we can guess a new force is acting upon it. So the “strength” of the net has somehow changed under the influence of the weight of the apples. The latter is constant, so somehow the “strength” force has weakened. It is this “weakening” bit I don’t really understand. I guess the “strength” force is really a sum of lots of forces which Physicists can examine. And I need to understand 😉
    Thanks again

    • The Professor says:

      Hi Eddie, You are correct in your assumption that the strength of the net has changed. The strength of the net is determined by the local strength of the fibres which make up the net. These fibres are under different local stress (read this as local forces) and therefore some will be closer to failure than others. The force of the apples is constant but some of the fibres of the net can slowly start to fail under this constant force. Once one of them has failed the net becomes progressively weaker until it suddenly loses all strength as the net splits apart. You had good instinct in explaining the failure. Best of luck in your studies.
      Regards Mac.

  6. Malvina Pushkova says:

    Hi, prof.Mac!
    I’m from Russia, thus sorry if my English is not very good. I intensively learn English and I’m keen on physics. I don’t have iPhone, iPad or iTunes therefore I only have watched all your videos on YouTube. It’s very interesting project! Wish you success!!

  7. Deep says:

    Thanks Professor Mac for all your helpful videos so far. Keep up the great work!

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