Question

Find acceleration of block $A$ and $B$. If $\mu_{1}=0.8$ and $\mu_{2}=0.4$

• A. $0\, m / s ^{2}$ and $0\, m / s ^{2}$
• B. $1 \,m / s ^{2}$ and $1 / 2\, m / s ^{2}$
• C. $2 \,m / s ^{2}$ and $0 \,m / s ^{2}$
• D. $1 / 2 \,m / s ^{2}$ and $1 / 4\, m / s ^{2}$

Answer 1

Answer: (C)

Limiting friction between $B$ and ground
$=0.4(5+10)(10)=60\, N$
$\Rightarrow $ acceleration of $B$ is zero.
acceleration of block $A$.
$a_{A}=\frac{50-0.8(5)(10)}{5}=2\, m / s ^{2}$
In this case lower block can not move at all.