Question

Two blocks A & B with mass 4 kg and 6 kg respectively are connected by a stretched spring of negligible mass as in figure When the two blocks are released simultaneously the initial Smooth acceleration of B is 1.5 m/s2 westward. The acceleration of A is:

Answer 1

Final Answer : $9/4 m/s^2$ eastward.

Steps:
1) Since, External Force on (Spring + A + B) system is 0.
$=> a_{cm} = 0 \\ => \frac{m_Aa_A+m_Ba_B}{m_A+m_B} =0 \\ => 4 * a_A + 6* 1.5 = 0 \\ => a_A = -\frac{9}{4} m/s^2.$

Hence, Acceleration of A is $9/4 m/s^2$ eastward .