Professor Mac Explains Newton's Second Law of Motion

Newton's Second Law of Motion. Join Professor Mac as he demonstrates the use of Newton's Second Law in the form "Force equals mass times acceleration" in a series of beautifully animated experiments.

You can own a copy of the video together with an explanation of the law in five easy to understand steps when you purchase Professor Mac's ebook available for the iPhone and iPod touch at:

In this video, Professor Mac explains Newton's second law of motion. This is one of three laws published by Sir Isaac Newton in 1687.

Professor Mac demonstrates the use of the law in the form "Force equals mass times acceleration". He conducts three experiments where he uses different forces to accelerate wooden blocks along a frictionless surface. By observing the positions of the blocks at one second intervals he is able to demonstrate the way in which force and mass affect the acceleration of an object. He also uses his tablet to work through examples of the use of the equation F=ma to predict acceleration and force.

For a tutorial summarising this video and further explanation of the law please visit the website:

[LearnwithMaconline]

Thank you Sara for letting me know. I'm pleased you found it helpful. I am currently preparing a video on the third law which will be released in the near future. I am interested to know how your teacher used it as part of the lesson? Was it shown to everyone at the same time or part of individual study activity?

Regards

Mac

[LearnwithMaconline]

Shubhom, Sorry I can't reply directly to your question as I don't think you have enabled the option on your account to receive comments. The object will only accelerate while a net unbalanced force is applied. So if you push the block it will accelerate while the push is active on the object. As soon as you stop pushing it the block will no longer accelerate. It will continue to have velocity but not acceleration. Mac

[BobFranceFishing]

Thank you Mac this was very helpful. I got a 100 on my test thanks to you! ;) just wanted to say thanks.

[LearnwithMaconline]

Hi Oshyrath. When using equations it is important to define what the variables are. Your point is that in Newton's Second Law of Motion the force we refer to should be the net force. This is calculated by summing the forces on the body under consideration remembering that the direction of the force must be taken into account during this summation. As long as we define F in F=ma as the net force then it is OK to use F=ma. You can also express the equation as you have suggested. Regards Mac

[derekperkins]

I appreciate the huge amount of work that has gone into this video- congratulations.

[LearnwithMaconline]

The symbol is used to indicate the summation of the forces. It is the upper case letter Sigma from the Greek alphabet. We use this symbol as a quick way to indicate summation when writing equations.

Mac

[LearnwithMaconline]

Hi Trojan. Good question. One way would be to apply the 50N force to the large block and measure the acceleration achieved. If friction was present the acceleration would be less than the 1m/s2 that was calculated. If you measured the actual acceleration achieved you can calculate the force that was accelerating the block from F=ma. The difference between this calculated force and the 50N applied force is the friction force. Mac

[sanjnathiru]

Thank you so much Mac..I understood very well the concept of second law....

[LearnwithMaconline]

Hi Amie. It is good that you are thinking carefully about the direction of the force since this is important when analysing forces. If you pull an object towards you it will move towards you since it moves in the direction of the pull force. Similarly if you push the object away, it will move away from you as it moves in the direction of the push force. Have I understood your question correctly?

Regards Mac.

[LearnwithMaconline]

Hi Bobby, I can't reply to you directly as you don't have that option selected on your account. Thanks for letting me know about your test result. Well done. Mac

[LearnwithMaconline]

Hi Vonti, I understand why it is confusing. The reason the time is squared is: Velocity is defined as a distanced travelled per unit time. Hence the use of m/s. Acceleration is a change in velocity per unit time. Hence we have change in velocity (m/s) per unit time (s). So acceleration is m/s/s which is m/s^2. For constant acceleration the distance travelled changes with the square of the time. You calculate this using the equation distance= 0.5at^2 assuming the initial velocity is zero. Mac

[baskar]

Thank you sir for the reply and the clarity, conveinced almost

[NaramZiady]

I got a 100 on my physics test thanks to this I love u

[seanbarrett]

I had a hard time understanding Newton's 2nd Law of Motion during lecture. The way you were able to simplify everything really helped. Thanks for uploading the awesome video Mac!

[LearnwithMaconline]

Hi Nicolaus. You have good instinct here. However the quantity you are discussing is energy - kinetic energy to be precise. In both cases you have the same car moving with the same velocity and this means it has the same kinetic energy which is defined as 0.5 times mass times velocity squared (similar to what you are suggesting). Acceleration relates to how quickly it achieved this velocity. The larger the acceleration the larger the force required for a given mass of car hence F=ma.

Mac

[sohailbutt]

Great video thankyou .
I really understood the Newton second law.

[LearnwithMaconline]

Hi Jason, thanks for your comment. You are right. If the acceleration is zero then it tells us that the forces are in balance. The reason for the exercise was to demonstrate how to use F=ma to calculate acceleration. In the case of the block on the table it is zero. We would use the same analysis approach to calculate a non zero acceleration for the situation where an unbalanced force was active. The zero acceleration case is a good check since it is an obvious result. Regards Mac

[xpalefectx]

Everyone is probably here for a homework but I'm here because my teacher isn't good at explaining and I have a quiz in about 15 hours

[LearnwithMaconline]

Thank you for your feedback Eman. I'm pleased you like them.

Regards Mac

[ThaMasterSniper]

Thank you for this video! It helped me understand Newtons second law of motion much easier.