# Two masses of $10\; kg$ and $20\; kg$ respectively are connected by a massless spring. A pull of $100 N$ acts on the mass $20 kg$. If the instantaneous acceleration of 10 kg mass is $2 m/s^2$, what is the acceleration of $20 kg$ mass

$(a)\;1 m/s^2 \quad (b)\;2 m/s^2 \quad (c)\;3 m/s^2 \quad(d)\;4 m/s^2$

## 1 Answer

Force on $10 kg$ mass =ma
$\qquad= 10 \times 2$
$\qquad=20 N$
Free body diagram
=> $K_x=20 N$
Therefore Force on $20 kg$ mass
$\qquad=100-k_x$
$\qquad= 100-20$
$\qquad=80 N$
$a_2=\large\frac{F}{m}$
$\quad=\large\frac{80}{20}$
$\quad=4 m/s^2$
Hence d is the correct answer.

answered Jul 4, 2013 by
edited Jan 26, 2014 by meena.p

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