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

[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. :)

 

[nil1996]

about a

can you specify which block has acceleration 'a'.

 

[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. :(

 

[nil1996]

a

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

 

[shin777]

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

 

[nil1996]

explanation

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

solve these to find "a".

 

[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?

 

[nil1996]

reply

do you know the Newtons second law.
ƩF_x=ma_x
ƩF_y=ma_y

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

 

[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

 

[nil1996]

yes

yes it is 15/4 only

 

[nil1996]

yes

thats correct