# Can you help me find what a = on this problem?

1. Jun 3, 2013

### shin777

Sorry about bad picture. I did best I could but I am not sure that's how I do this problem.
If I am wrong can you give me right equations for this? Thank you. :)

Last edited: Jun 3, 2013
2. Jun 3, 2013

### nil1996

can you specify which block has acceleration 'a'.

3. Jun 3, 2013

### shin777

i have no clue. That's how my teacher wrote the problem as take home problem. He just had pictures and what is a = ? I think he meant total acceleration. He gave us similar problems few weeks ago but it was on two boxes without mk instead of box and triangle with mk. So I used formula to find acceleration of each blocks and found T1 and T2 and then applied to same formula he used on the problem he did few weeks ago. :(

4. Jun 3, 2013

### nil1996

a

a should be 15/4.
(i used g=10 not 9.8)
the acceleration of each block is the same.

Last edited: Jun 3, 2013
5. Jun 3, 2013

### shin777

hmm.. 15/4? how did you end up with that?

6. Jun 3, 2013

### nil1996

explanation

T1=10a
T2-10gsin30=10a
20g-(T1+T2)=20a

solve these to find "a".

7. Jun 3, 2013

### shin777

err.. I can't really tell how your equation works with that 3 short equations. Did you use mk = .1 and mk = .2 on each side to get the answer?

8. Jun 3, 2013

### nil1996

do you know the newtons second law.
ƩFx=max
ƩFy=may

first draw the free body diagram of each block and then apply these eqns to get my above eqns

9. Jun 3, 2013

### shin777

but you sure it's 15/4 not 15/40? when I plug in my t1 and t2 and solve for a using your 3 line equation, I get 15/40

10. Jun 3, 2013

### nil1996

yes

yes it is 15/4 only

11. Jun 3, 2013

### nil1996

yes

thats correct