Question

Three blocks on a frictionless horizontal surface are in contact with each other as shown in the figure below. A force F is applied to block A (mass mA ). Determine the acceleration of the system (in terms of mA , mB and mC).

Answer 1

If, pushing block A, we also push blocks B and C, the acceleration of the system will be

$$a=\frac{F}{m_a+m_b+m_c}$$

because the force is actually applied to all three blocks.