Question

Find the contact force between the $3kg$ and $2kg$ block as shown in the figure.

• A. $75N$
• B. $25N$
• C. $55N$
• D. $45N$

Answer 1

The correct option is C $55N$

Considering both blocks as a system to find the common acceleration



$F_{net}=F_1-F_2=100-25=75N$
Common acceleration $a=\frac{F_{net}}{5kg}=\frac{75}{5}=15m{s}^{-2}$
To find the contact force between A & B, we draw F.B.D of $2kg$ block.



From $(\Sigma F_{net}{)}_x=ma$
$N-25=2\times 15$
$\Rightarrow N=55N$