Question

In the figure given below $(g=10{\text{m/s}}^2)$, acceleration of $2\text{kg}$ block is :

• A. $2{\text{m/sec}}^2$
  
• B. $4{\text{m/sec}}^2$
• C. $6{\text{m/sec}}^2$
• D. $8{\text{m/sec}}^2$

Answer 1

The correct option is A $2{\text{m/sec}}^2$


$\text{FBD}$ of system
$a_{1kg}=a_{2kg}=a_{3kg}=a\left(let\right)$
By the balancing of force,
$F_1-(mg\sin {30}^{\circ }+F_2)=ma$
where $m$ is the total mass of the system.
$60-(30+18)=6a$
$12=6a$
a = $2{\text{m/s}}^2$

Why this question? Note: Since the masses move keeping contact with each other, the acceleration of the system is equal to the acceleration of the individual masses.