1. Feb 6, 2013

### lioric

1. The problem statement, all variables and given/known data
In figure, the pulleys and the cod are light, all surfaces are frictionless, and the cord does not
stretch.
a) How does the acceleration of block 1 compare with the acceleration of block 2?
The mass of block 2 is m2 = 1.3 kg. Derive an expression for the acceleration of the
block having mass m2 as a function of the mass of block 1, m1.

2. Relevant equations
mg-T=m2a2
T=m1a1=m12a2

3. The attempt at a solution

The first one (a) i have done.
Which is that due to the pulley the acceleration of a2=1/2 a1

Can some one help me with the b part

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Last edited: Feb 6, 2013
2. Feb 6, 2013

### Staff: Mentor

Re: Some one plz help me with the derivation

Hi lioric. Is there supposed to be a diagram to accompany this?

3. Feb 6, 2013

### lioric

Re: Some one plz help me with the derivation

sorry i was in a rush and forgot
now its there

4. Feb 6, 2013

### lioric

Re: Some one plz help me with the derivation

This is what i got for the derivation. But something is not right

5. Feb 6, 2013

### lioric

Re: Some one plz help me with the derivation

Mass 2 equation
The pulley give 2 tensions so 2T
m2g-2T=m2a2

Mass 1 equation

T=m1a1
since a2 = 1/2a1
a1= 2a2

T=m12a2

substitute mass 1 equation in mass 2 equation as T

m2g-2(2m1a2)=m2a2
m2g-4m1a2=m2a2

make subject a2

-4m1a2-m2a2=-m2g
change negative sign by multiplying by -1

4m1a2+m2a2=m2g

a2(4m1+m2)=m2g

a2=m2g/4m1+m2

But i feel that this is not right.

6. Feb 6, 2013

### haruspex

Re: Some one plz help me with the derivation

It's cog, not cod.
That equation is not correct. What are all the forces on m2?

7. Feb 6, 2013

### lioric

Re: Some one plz help me with the derivation

m2 would have gravity and tension

8. Feb 6, 2013

### Staff: Mentor

Re: Some one plz help me with the derivation

I believe it's c-o-r-d

9. Feb 6, 2013

### lioric

Re: Some one plz help me with the derivation

ok enough about the "CORD"

m2 would have gravity and tension those are the forces on M2

so whats next?

10. Feb 6, 2013

### haruspex

Re: Some one plz help me with the derivation

That's better (your post crossed with mine).
Looks ok to me, if parentheses inserted:
a2=m2g/(4m1+m2). What bothers you?

11. Feb 6, 2013

### lioric

12. Feb 6, 2013

### haruspex

The two are equivalent.

13. Feb 9, 2013

ok thank you