Question

Two 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 $12\, m / s ^{2}$. What is the acceleration of $20 \,kg$ mass?

• A. $12\,m / s ^{2}$
• B. $4 \,m / s ^{2}$
• C. $10\, m / s ^{2}$
• D. Zero

Answer 1

Answer: (B)

As the mass of $10\, kg$ has acceleration $ 12\,m/s^{2} $ ,
therefore it applies $ 120\,N $ force on mass $ 20\,kg $ in a backward direction.
$ \therefore $ Net forward force on $ 20\,kg $ mass
$ =200-120=80\,N $
$ \therefore $ Acceleration $ =\frac{80}{20}=4\, m/s^{2} $