State Newton’s third law.
A block X with mass $m_x$ moves in a straight line across a horizontal frictionless surface, as shown in Fig. 3.1. It travels at speed $5v$ and collides head-on with a stationary block Y of mass $m_y$. After the impact, the two blocks stick together and continue with a shared speed $v$, as shown in Fig. 3.2.
Use conservation of momentum to show that the ratio $\frac{m_y}{m_x}$ is $4$.
Calculate the value of $\dfrac{\text{total kinetic energy of X and Y after collision}}{\text{total kinetic energy of X and Y before collision}}$.
State the ratio in (ii) for a perfectly elastic collision.
The momentum of block X in (b) varies with time $t$ as shown in Fig. 3.3. Block X comes into contact with block Y at $t = 20\,\text{ms}$.
Describe, qualitatively, the magnitude and direction of the resultant force, if any, acting on block X over the time interval $t = 0$ to $t = 20\,\text{ms}$.
Describe, qualitatively, the magnitude and direction of the resultant force, if any, acting on block X over the time interval $t = 20\,\text{ms}$ to $t = 40\,\text{ms}$.
On Fig. 3.3, sketch the variation of the momentum of block Y with time $t$ from $t = 0$ to $t = 60\,\text{ms}$.