Q. The masses of $10\ kg$ and $20\ kg$ respectively are connected by a massless spring as shown in figure. A force of $200\ N$ acts on the $20\ kg$ mass. At the instant shown, the $10\ kg$ mass has acceleration $12\ m/\sec^{2}$. What is the acceleration of $20\ kg$ mass
A) $12\ m/\sec^{2}$
B) $4\ m/\sec^{2}$
C) $10\ m/\sec^{2}$
D) Zero
Explanation
(b) As the mass of $10\ kg$ has acceleration $12\ m/s^{2}$ therefore it apply $120N$ force on mass $20kg$ in a backward direction
$\therefore$ Net forward force on $20\ kg$ mass $= 200 - 120 = 80N$
$\therefore$ Acceleration $= \frac{80}{20} = 4\ m/s^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.