Answer
The block's acceleration is $2.35m/s^2$
Work Step by Step
(i) Newton's 2nd Law of Motion provides the most useful way to determine the acceleration $a$ of the block. $$\sum F=m_{block}a$$
(ii) There are 2 forces in the x direction:
- Tension force in the rope $T$, which pulls the block rightward.
- Kinetic friction $f_k$, which opposes that rightward motion.
Therefore, $\sum F=T-f_k$ and $\sum F$ does not equal just $T$.
(iii) According to Newton's 2nd Law: $$\sum F=T-f_k=m_{block}a$$
We have $T=24N$ and $m_{block}=\frac{88}{9.8}\approx9kg$
There is no vertical motion, so normal force $F_N$ equals the block's weight on the moon: $F_N=mg_{moon}=9\times1.6=14.4N$
Therefore, $f_k=\mu_k\times F_N=0.2\times14.4=2.88N$
So, $$a=\frac{T-f_k}{m_{block}}=2.35m/s^2$$
