Newton's 2nd Law (10 of 21) Calculate Acceleration w/o Friction; Table, Pulley, Two Masses

Shows how to calculate the acceleration of a two mass system using Newton's Second Law. One of the masses is on a frictionless table and the other hangs off the end of the table over a pulley.
The acceleration of an object is directly proportional to the net force applied to the object and inversely proportional to the mass of the object. The second law can also be stated in terms of an object's changing momentum, such that the rate of change of momentum of an object is directly proportional to the net force applied and the change in momentum is in the direction of the net force.
You can see a listing of all my videos at my website, www.stepbystepscience.com.
Link to share this video: • Newton's 2nd Law (10 o...
Please support my channel by doing all of the following;
(1) Subscribe, get all my physics, chemistry and math videos
(2) Give ma a thumbs up for this video
(3) Leave me a nice positive comment
(4) Sharing is Caring, share this video with all your friends

[@MotoMechzorz]

Just wanted to let you know that years down the road you are still helping people. My class uses 'active learning' which means you read the book and teach each other in class, no lectures. It's going as well as you would expect. Without your videos I would be screwed right now, thank you!

[@nikopatrikios568]

You might be my life saver for AP Physics this year

[@stepbystepscience]

Hope it goes well in AP physics...You can see a listing of all my videos at my website, www.stepbystepscience.com

[@rileybrown5039]

Everyone who did problems like this made it wayyyy more complicated. After searching forever this is the first video that makes sense and made me understand why you do this. Thank you!

[@stepbystepscience]

Thank you very much for the nice comment.

[@stepbystepscience]

Munchar Cassell, Good question, but in this case, as I stated at the beginning of the video, there is no friction between M1 and the table. It the link below I go over the case where there is friction between M1 and the table.
th-cam.com/video/SBRyluYjqxY/w-d-xo.html

[@pccasdengroup8379]

this was well explained and it was very helpful because i have a test today on similar problems

[@tiasantos4724]

Thank you so much. This video was short and sweet and to the point and it helped me understand a lot. Definitely thumbs up.

[@stepbystepscience]

great, thanks for commenting.

[@maya.b5704]

Thank You so Much 😊, you really helped me understand this lesson .

[@fletcherriches1385]

Thanks for the video!! It helped me understand how to do these problems. Super helpful!

[@stepbystepscience]

You are very welcome and thanks for commenting.
You can see a listing of all my videos at www.stepbystepscience.com

[@nickitheboss9516]

He devotes himself to teaching GREAT TEACHER Thank you

[@angelafidler5796]

OMG thank you so much!!! Helped me out so much!✌🏼👌🏼

[@rileynobles7146]

Awesome job!! Very understandable.

[@warpingz5533]

You're a big help. Our midterms is coming. I've watched this and it helps me to understand more about this Newton's law

[@stepbystepscience]

Hope the mid term goes well...You can also see a listing of all my videos at my website,www.stepbystepscience.com

[@vihanamarasinghe1102]

THANK YOU SO MUCH

[@euclasew]

thank you so much, I'm studying this now for IB HL and my physics teacher is terrible and I can't understand a word she says. Thank you so much for posting this, I now understand it

[@stepbystepscience]

Thanks for the comment hope all goes well, You can see a listing of all my videos at my website, www.stepbystepscience.com

[@onyxclarke]

Thank you so much! Big help in understanding this type of problem.

[@stepbystepscience]

Great and thanks for the comment.

[@ZK-nb3cq]

Great simple, to the point explanation!

[@stepbystepscience]

+Zunair khan Thanks for the comment, yes I try to get right to the point.
You can a listing of all my videos from my website, www.stepbystepscience.com

[@samechen9312]

Thank you. You really help me to deal with this kind of the problem.

[@stepbystepscience]

You are so welcome!

[@shelbychapa]

THANK YOU! This is awesome!

[@imrickiee4651]

my pro always uses that some of the equations to add them up and use the Substitute method in the end . then get the acceleration. very complicated and can't understand!!! your ways are very easy！！！！ and I understand at all!!!! thanks!!!!!!!!!

[@stepbystepscience]

Great that you found the video to be helpful.

[@gabrieljacobs6115]

im watching this in 2017. this helped so much.

[@miki4117]

This talk is in principle wrong and confused although the result is correct! Forces are vectors

[@stepbystepscience]

It is not wrong, there is just more than one way to solve the problems.

[@Saucemeurshordy]

thanks alot really helped me

[@nazb4023]

Amazing , thank you!!! Love your videos

[@stepbystepscience]

Thank you so much for watching and commenting.

[@bluerain4866]

How would you be able to use the acceleration of system to find the change in velocity using f= m(vf-vi/s) because when I do it I get the wrong velocity?

[@spacepopeXIV]

You sound like if Vince Vaughn was a physicist, and I like that very much.

[@stepbystepscience]

I have not had the Vince Vaughn comment for a while, thanks and I am glad that you like it.

[@justblaze4707]

Thank you very much!

[@ianpaulguanzon375]

Thanks for your videos. Well appreciated! :)

[@stepbystepscience]

You are very welcome, thanks for commenting.

[@notyourneighbor3416]

Why is my teacher complicating things ugh

[@stepbystepscience]

I try to keep it simple and go over everything step-by-step. You can a listing of all my videos from my website at www.stepbystepscience.com

[@BanterlordHades]

How would this problem change if the string was connect to a pulley on m1 and looped around it and was held in place by a wall?

[@chrischanty569]

Absolutely fantastic explanation!

[@stepbystepscience]

Glad you think so!

[@bayleyspencer8617]

loving these videos, only reason i've passed maths and engineering at uni was youtube

[@stepbystepscience]

Great and thanks for letting me know.

[@ShivamPatel-hl9ys]

thank you so much you helped with my half Atwood project for my online ap physics i am so lost on how to do it

[@stepbystepscience]

No problem, glad that you found the video helpful.

[@laurybabii]

This has helped me so much. Thank you

[@stepbystepscience]

You're very welcome and thanks for commenting.

[@laurasofia1483]

Thank you!! It helped a lot! :)

[@stepbystepscience]

Laura Sofia you are very welcome, glad it helped and thanks for commenting.

[@1105comfortablynumb]

Extremely helpful. Thanks.

[@stepbystepscience]

Great, thanks for letting me know.
You can see a listing of all my videos at www.stepbystepscience.com

[@latakumari6083]

Thanks 🙂🙂🙂u cleared my doubt very well and reduced the weight of my mind. 😃

[@stepbystepscience]

Glad to hear that. Thanks for the comment.

[@alondrachavez8380]

i love you you saved my life thank you very much
sincerely,
Amellalli and Alondra

[@stepbystepscience]

+Alondra Chavez You are very welcome. You can see a listing of all my videos at my website,www.stepbystepscience.com

[@porkyp1845]

Is N=mg true at any speed? But what if its hanging mass is speeding up as it falls?

[@MohamedMohamed-su7zm]

i would could give you more than one thumbs up i really like your videos thank you so much

[@stepbystepscience]

That is very nice of you to say, thanks. You can see a listing of all my videos at www.stepbystepscience.com

[@aaravkansal4174]

How would I find coefficient of friction if I was given acceleration

[@kathyacardona9964]

Thanks for the video!

[@stepbystepscience]

Kathya Cardona You are very welcome, thanks for commenting.

[@liamo890]

Thanks homie!

[@kookiemingyu175]

Hello for the using Newton’s 2nd Law of motion to the 2nd mass whew in Ft = m2g - m2a inputing the values we get Ft=(4kg)(-9.8) - (4kg)(3.56m/s^2) why do I get an answer -53.44 instead of 24.9N? Please answer ASAP!! Thank you.

[@pressed4888]

how do you find the net force provided by the hanging mass?

[@MelvilPon]

Awesome video 🇵🇬🇵🇬all the way from Papua New Guinea

[@stepbystepscience]

Thank you so much and greetings from Berlin, Germany!

[@MopTopRock]

Thanks ! Using the systems approach is much easier

[@stepbystepscience]

MopTopRock Great, glad that you found the video helpful. Thanks for commenting.

[@avneetkaur1518]

Great teacher!

[@stepbystepscience]

Glad you think so, thanks!

[@jhay_mstv6331]

what about if it gives a coefficient friction of m1?

[@brawlpaz6120]

ty this helps a lot

[@stepbystepscience]

glad to hear that, thanks for watching!

[@debdattabhattacharya6254]

How are you adding forces which are in different axes ? the mg and Ft on m2 are in the y axis while the other Ft on m1 is in the x axis.

[@stepbystepscience]

Really the end result is that the force is on the same axis, the pulley just changes the direction of the force. You can see a listing of all my videos at my website, www.stepbystepscience.com

[@andreslopez-reyes3852]

THANK YOU YOU'RE THE BEST

[@stepbystepscience]

Very nice of you to say, thanks.

[@ercfs]

Mantap jua

[@aaryadeshpande1621]

5:13: I have a question. What if we considered the downward to be negative? Then how would it work? Because then in that case for the equation to still hold true, wouldn't then Ft have to cancel out with m2g (and so they would need to be equal)? How would it work out? Thank you!!

[@stepbystepscience]

It basically works out the same, the acceleration would just be negative but the magnitude (number ) would be the same.

[@mariaalexandrafontanilla2676]

Thank you for saving my life again

[@stepbystepscience]

You are very welcome! Thanks for the comment.

[@DUMPL1NGZ]

Thank you so much

[@stepbystepscience]

You're most welcome

[@shaikhaaldhaheri3820]

For the net force do i still just pick one of the masses and multiply it by the acceleration we found or do i need to add both masses and multiply it to acceleration?

[@stepbystepscience]

For the net force you just need add up all of the forces.

[@santiagopenaloza8924]

Thank you soooo much i have a test tomorrow at 7am

[@stepbystepscience]

You're welcome. Best of luck on the test!

[@somenerdyblonde]

How do you know which way the acceleration is supposed to go? Why would a lighter block pull a heavier block of a table? I have a problem like this where a car is raising a dangling weight, so the acceleration should be the opposite, and I'm very confused.

[@stepbystepscience]

The lighter block pulls het heavier block because it is hanging off the edge of the table. As far as the car goes I would have to see the problem but everything is probably just opposite.

[@mehakimran4045]

KINGGGGGG SLAYYYYY

[@abednegovidolo7665]

very thankful

[@stepbystepscience]

You are most welcome

[@rajnishkumar4249]

Thank you and i got it ...

[@stepbystepscience]

Awesome!

[@agusspermata4600]

I am a retiree....i still want to understand the law .. F = ma
Really interesting topic....please create more videos on this topic....TQ..

[@stepbystepscience]

Thanks for the suggestion. Check out all 26 of my videos on this topic.

[@millions2nette]

Please clear up the m2a part. I understand m2g is the mass of m2 times gravity, but what is the m2a. Very close to the end of the vid, its, Ft=m2g-m2a. What is the m2a. I was thinking, it cant be the m2 mass, because isnt that covered by m2g? Please answer. Gotta test soon. Thanks

[@stepbystepscience]

I think the short answer might be that m2a is the mass of m2 times the acceleration....the acceleration we found at the end of the previous slide a = 3.56 m/s2). At this point you are trying to find the force of tension in the string (FT). So you apply Newton's second law to mass number 2.....F = ma. The are two forces, the weight and the tension force. Then there is the ma part. The mass is given and the acceleration is found at the end of the previos slide. Now you can solve for FT. Does that help? Hope the test goes well!

[@arminmollahajlou5904]

simply perfect 👌 👌

[@stepbystepscience]

Thanks

[@healing-hero9792]

Thanks!

[@stepbystepscience]

You are very welcome!

[@ibrahimkhan492]

can you please explain tension and acceleration when bodies are accelerating and non accelerating.

[@stepbystepscience]

That might take awhile.
You can see a listing of all my videos at www.stepbystepscience.com

[@RahulKrRY]

Very Nice...

[@stepbystepscience]

Thank you! Cheers!

[@jimmyohara2570]

Thank you soo much

[@stepbystepscience]

You are very welcome, thanks for commenting!

[@nadianoormohamed4432]

WHY IS THE FORCE OF TENSION OF M1 POSITIVE ISN'T IT OPPOSITE TO THE MOTION?

[@stepbystepscience]

+Nadia Noormohamed Because we designated to the right and as positive and the tension vector points to the right. The tension force is what is causing the object to move to the right. It is pulling the object to the right. The friction force for m1 is opposite of the motion, to the left.
You can see a listing of all my videos at my website,www.stepbystepscience.com

[@danielsammy6286]

Great 👍

[@stepbystepscience]

Thanks!

[@marlon123444]

thank you so much...

[@stepbystepscience]

you are very welcome.

[@aleoghenamaxwell4296]

Thanks so much

[@stepbystepscience]

Thanks for letting me know. Thank you for saying so, You can see a listing of all my videos at my website, www.stepbystepscience.com

[@DylanGames1000]

Or you could simply just multiply the product of m1 and m2 and divide that product by the sum of those two forces. Multiply all that by 9.8 m/s^2

[@danielbailey3291]

But what if m2 mass was not given but you were given time it took to fall and the height of m2

[@stepbystepscience]

Sounds like you could calculate the acceleration first and then get m2.

[@spokes_the_comedian]

It just became very easy, my teacher was giving me funny methods of doing it

[@stepbystepscience]

Great, step by step.

[@eliscassell4991]

they should be friction for M1 to the left!? am i right

[@mujahidsyed2917]

generally yes, but this problem we are neglecting friction

[@Hbrand03]

what if my sum of forces equation has friction and I don't know the value of it?

[@stepbystepscience]

You can calculated it, if you know the normal force and the coefficient of friction.

[@Hbrand03]

@@stepbystepscience thank you!

[@Hearty-Chan]

What if there are three masses on the table and
m1= m2 = m3

[@stepbystepscience]

Then typo do the same thing for each mass.

[@monicaarnaout]

i still dont understand how you made M2g positive and Ftension in the y direction negative?

[@stepbystepscience]

I decided the way that the object will move is the positive direction. M2 moves down so that is positive, the tension force points in the opposite direction (up) so that is negative. You can see a listing of all my videos at my website, www.stepbystepscience.com

[@monicaarnaout]

okay thank you! so would it have worked if you decided down was negative?

[@stepbystepscience]

+acinom yes as long as you are consistent through out the problem.

[@monicaarnaout]

awesome, thanks for responding!

[@user-iu7qg9lo7y]

these messy problems need to be explained by an elegant mind such as yours, otherwise it gets more complicated.

[@stepbystepscience]

Step by Step explanation.... thanks for watching and commenting. Very nice of you to say.

[@farahjamal3257]

what if the string is suddenly broken? what will be the acceleration of mass 1?

[@stepbystepscience]

is it already moving, is there friction. if not friction and already moving then it would remain constant. does that help?

[@farahjamal3257]

@@stepbystepscience yeah i got it.. thank you very much

[@lilakohis]

if i pass physics im buying one of your shirts

[@stepbystepscience]

That's awesome, good luck!

[@mickytube1935]

6:54 it must be added rather than subtracted

[@kookiemingyu175]

Hello, I am having problems with that part. The sign should be negative because the it was moved to the other side. But Indeed, I do not obtain the correct answer when it is subtracted as stated on the video but when I add it I get a negative -24.9 (wherein it is positive on the video). Please help

[@rl_flocky1462]

My teacher slove the same equation but it's a different answer

[@stepbystepscience]

There are different ways to do it but you get the same answer.

[@rl_flocky1462]

@@stepbystepscience yes you're right. Sorry I was wrong. Because I have seen of you other videos and it was the same equation and the same answer.
You are really good and we need people like you.
I'm sorry again.

[@yamackocovali8075]

Why dont u calculate the FN?

[@stepbystepscience]

I assume mean the FN as the normal force. If I did not calculate the normal force it is because you do not need it to calculate the acceleration. It does not act along the direction of motion. Does that help?

[@yamackocovali8075]

@@stepbystepscience yes it does , thanks
Do uhave these types of exercises but with friction?

[@stepbystepscience]

@@yamackocovali8075 Yes, I generally do a video without friction and then one with friction. Here is the link to the with friction video: th-cam.com/video/SBRyluYjqxY/w-d-xo.html

[@matthewventus5452]

cool beans

[@iKingOf]

no, thank you

[@stepbystepscience]

But why not?

[@iKingOf]

@@stepbystepscience I realize now how my comment may have been poorly thought out & confusing.
What I meant was "Thank you the video was amazing & very helpful."

[@kidflyer13]

this dude sounds like vin diesel

[@stepbystepscience]

Either him or Tom Hanks but some times Vince Vaughn...

[@caitlinyuen5140]

here in 2020 check

[@jenansamannaz4871]

My teacher taught this the harder way. I am failing physics cos of my teacher

[@stepbystepscience]

TH-cam can be helpful. A different perspective. You can see a listing of all my videos at my website, www.stepbystepscience.com

[@richarc2307]

Cosine

[@seanbig859]

You are a beautiful man and I just wanted you to know that