Question

Five identical cubes each of mass $m$ are on a straight line with two adjacent faces in contact on a horizontal surface as shown in the figure. Suppose the surface is frictionless and a constant force $P$ is applied from left to right to the end face of A; which of the following statements are correct?

• A. the acceleration of the system is $\frac{5P}{m}$
• B. the resultant force acting on each cube is $\frac{P}{5}$
• C. the force exerted on D due to C is $\frac{2P}{5}$
• D. the acceleration of the cube $D$ is $\frac{P}{5}m$

Answer 1

The correct option is B the resultant force acting on each cube is $\frac{P}{5}$

Acceleration of the system,

$\overrightarrow{a}=\frac{P}{5m}$

FBD of each body implies,

$\Rightarrow P-F_{AB}=m\overrightarrow{a}\Rightarrow F_{BA}-F_{BC}=ma\therefore F_{BC}=\frac{3}{5}P(\because F_{AB}=F_{BA})$

Similarly,

$F_{CD}=F_{DC}=\frac{2}{5}P\&F_{ED}=\frac{1}{5}P$

Net force on each cube,

$F_{net}=m\overrightarrow{a_{net}}=m.\frac{P}{5m}\therefore F_{net}=\frac{P}{5}N$