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asset567 asset567
wrote...
Posts: 3
Rep: 0 0
2 years ago

A mass m1 = 5.4 kg rests on a frictionless table and connected by a massless string to another mass m2 = 4.5 kg. A force of magnitude F = 37 N pulls m1 to the left a distance d = 0.7 m.

1. How much work is done by the force F on the two block system?
I got 25.9 J which my homework system thinks is correct.
 
2)How much work is done by the normal force on m1 and m2?
0 J seems to be right here

3)What is the final speed of the two blocks?
2.2874 m/s seems to be correct here

4)How much work is done by the tension (in-between the blocks) on block m2?
cannot figure this one out

5)What is the tension in the string?
cannot get this one either

6)The net work done by all the forces acting on m1 is:
 positive seems to be right here

7)What is the NET work done on m1?
I am unfortunately unable to get this one either

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wrote...
Educator
2 years ago
Quote
5)What is the tension in the string?
cannot get this one either

7)What is the NET work done on m1? I am unfortunately unable to get this one either

For this, you will need to know that:

\[ work=force \times displacement \]

force: f
displacement: s
work: w
tension: t

Except there is a force acting on m1 because it is connected to m2 via a string, so we will subtract the tension from 37 N (given in the question). We subtract because the tension is going in the opposite way relative to the left where is moved:

\[ work = (f-t)\times d \]
\[ work = (37-t)\times 0.7 \;\;\;\;\; (1) \]

so now we need to find the tension...

Remember that tension is the same as force, so it can be calculated used newton's second law

\[F=ma\]

\[T=ma\]

\[a = \frac{T}{m} \]

\[ \frac{37}{5.4} = \frac{T}{5.4} - \frac{T}{4.5} \]

Solve for \(T\), you get:

\[T= 16.8 N \]

Now go back to equation \((1)\) and sub this in:

\[ work = (37-16.8)\times 0.7 = 14.1 N \]

Therefore, the net work done on \(m_1\) is 14.1 N
asset567 Author
wrote...
2 years ago Edited: 2 years ago, asset567
Forgive me for how this will likely sound, but would the last one not be in joules rather than Newtons?
Post Merge: 2 years ago

Also, that helped a ton, thank you immensely for your aid. I still am not sure how to figure out how much work tension does on mass 2. I think I do not understand how to account for it´s mass if that makes sense.

I apologize for how stupid I likely sound. I have been learning things before the teacher teaches us due to personal circumstances.
wrote...
Educator
2 years ago
Yes, my bad... \(N \cdot m\) is a Joule. Yikes
wrote...
Educator
2 years ago
I'm not entirely sure.

I believe the tension due to both strings is equal to the magnitude of the force, 37N.

Could you try 18.5 N times the 0.73 m?

Sorry to mislead you if you get it wrong.
asset567 Author
wrote...
2 years ago
That is not correct, no. But thank you for the rest of your help! Slight Smile
wrote...
Educator
2 years ago
Dang, as you can tell, physics isn't my forte. Feel free to post any further questions
wrote...
2 years ago
A mass m1 = 5.4 kg rests on a frictionless table and connected by a massless string over a massless pulley to another mass m2 = 5.6 kg which hangs freely from the string. When released, the hanging mass falls a distance d = 0.89 m

What is the tension in the string as the block falls?

What is the NET work done on m2?

For m1 :

=> T = m1 a

=> T = 6a ------- (1)

For m2 :

m2g - T = m2a

=> 3.3 (9.8) - T = 3.3 a -------- (2)

add up (1) and (2) u get :

=> 3.3(9.8) = 9.3 a

=> a = 3.48 m/s^2

from (1) T = 6a = 20.88 N

so W = Td = 20.88 (0.87) = 18.17 J <<<<<<<<
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