Question

Three blocks of masses 1 kg, 4 kg and 2 kg are placed on a smooth horizontal surface as shown in the figure. Two horizontal forces 120 N and 50 N are applied on the system. The acceleration of the system is

• A. $17.5m{s}^{-2}$
• B. $10m{s}^{-2}$
• C. $24.3m{s}^{-2}$
• D. $70m{s}^{-2}$

Answer 1

Answer: (B)

$10m{s}^{-2}$

Consider three blocks as a single block of mass $M=(2+4+1)=7kg$ and net force $F_n=120-50=70N$.
Thus, the acceleration of the system $a=\frac{F_n}{M}=\frac{70}{7}=10m/s^2$