Question

Depending on the mass of 4 kg, 10 kg and 3 kg, respectively, three bodies in a non-friction horizontal way

even at speeds of 5 m / s, 3 m / s, and 4 m / s (Figure). Collisions of bodies

then they are all connected and move to one side. Three-body system

Find the speeD

Answer 1

First, calculate when the 4 kg connects to 10 kg. Initial momentum: 4 kg moves at 5 m/s and 10 kg moving at 4 m/s. Final momentum: they both move at some speed. Find it:

$$4\cdot5+10\cdot3=(4+10)v,\\ v=\frac{4\cdot5+10\cdot3}{4+10}=3.57\text{ m/s}.$$

Then 14 kg move at 3.57 m/s and 3 kg at 4 m/s in one direction. It means that the 3 kg will never collide with 14 kg.