Adjacent Blocks: What is the mag of the force due m1 on m2?

[raven2783]

Homework Statement

Homework Equations

f=ma

The Attempt at a Solution

I got the acceleration by:

(f1-f2)/(m1+m2)=a

Now the first two q's I just cannot figure out.

1.5*4=nope
1.5/.367347*4=nope
1.5/.367347+4=nope
4*.367347=nope
2.66667-.647059=nope......ah!

 

[Redbelly98]

You're right that f=ma is the way to go here, and I agree with a=0.3673 m/s²***

Now that you know "a", and of course "m" for each mass, what does f=ma tell you about each mass?

***Uh, that should be written 0.37 m/s² when given as an answer. But keep those extra digits for doing calculations involving "a"

 

[raven2783]

f=ma
(m1)1.5
(m2)3.4
(a).367347
(m1+m2)=4.9
(m1-m2)=1.8

1.5*.367347=nope
4.9*.367347=nope
1.8+.367347=nope

lost.. what am i doing wrong?

 

[raven2783]

hmm..

 

[Redbelly98]

.. what am i doing wrong?

You seem to be plugging in numbers at random, and not thinking about what they mean.

In general, when you multiply a mass times its acceleration, that gives you ______ ? (No numbers here, use words.)

 

[raven2783]

it of course gives you force, the numbers represent my understanding of the words, I tried different combonations of adding subtracting and dividing mass, force and acceleration for the whole system but smartwork is telling me they are the wrong answers.

 

[raven2783]

i do appreciate your help btw thank you.

 

[Redbelly98]

You're welcome.

Yes, it gives you the force. And if there are 2 or more forces acting on the object, it gives you the net force.

Can you use the fact that you are really calculating net force on a mass, and get from there to what is being asked for?

 

[raven2783]

O.k. got it thanks!

the sum of the x forces is:

F-m1*a=3.4N

or

4N-(1.5kg*.367347m/s^2)=3.4N

and it is the same when you try the second mass:

F+m2*a=3.4N

or

2.2N+(3.4kg*.367347m/s^2)=3.4N

Thanks for your help.