Coefficient of kinetic friction between the two blocks

[Squeezebox]

Homework Statement

The coefficient of kinetic friction between the two blocks is 0.30. The surface of the table and pulleys are frictionless.

m₁=2 kg
m₂=3 kg
m₃=10 kg

Homework Equations

$$\Sigma$$F=ma
T₂-m₃g=m₃a
T₁-T₂=m₂a
friction-T₁=m₁a

The Attempt at a Solution

T₂=m₃g+m₃a
T₁=friction-m₁a

friction-m₁a-m₃g-m₃a=m₂a

(friction-m₃g)/(m₁+m₂+m₃)=a
a=-6.15m/s²

The answer in my book say it is -5.7m/s², though.

 

[method_man]

Homework Statement

The coefficient of kinetic friction between the two blocks is 0.30. The surface of the table and pulleys are frictionless.

m₁=2 kg
m₂=3 kg
m₃=10 kg
The answer in my book say it is -5.7m/s², though.

T₂=m₃g-m₃a
T₁=m₁a+m₁gμ
T₂=T₁+m₁gμ+m₂a
a=(m₃g-m₁gμ-m₁gμ)/(m₁+m₂+m₃)=5.7552