Question

Three identical
blocks, each having a mass $M$, are pushed by a force $F$ on a frictionless table
as shown in figure. What is the acceleration of the blocks? What is the net
force on the block $A$? What forces does $A$ apply on $B$ and $B$ apply on $C$?

Answer 1

R.E.F image

As all blocks are moving with

same acceleration (lefts say a) Then

$F=(mA+mB+mC)a$

$F=3Ma$

$a=\frac{F}{3M}$

By Newton's second law of motion

$\overrightarrow{F}net$ on a = mA a

$\overrightarrow{F}net/A=mAa=m\frac{F}{3m}$

$\overrightarrow{F}net/A=\frac{F}{3}$

As $\overrightarrow{F}net/A=F-N_1$

$\Rightarrow \frac{7}{3}=F-N_1$

$\Rightarrow N_1=\frac{27}{3}$

Fore on B by A $=N_1=\frac{27}{9}$

Fore on C by B $=N_2=m_{c}a$

$=M\frac{F}{3M}=\frac{F}{3}$