Inelastic collisions

Equipment

• Two virtual carts that stick together on a track
• Sliders for m₁, m₂, u₁, u₂ and interaction time
• Readouts of P and K before/after the collision

Procedure

1. Measure momentum before impact

   Set m₁ = 2 kg, m₂ = 3 kg, u₁ = 4 m/s, u₂ = −1 m/s. Before running, read "P before" and "K before", compute by hand $P = m_1u_1 + m_2u_2 = 5$ kg·m/s and $K_{before}$. Adjust "Interaction time" to see the collision play out fast or slow.

2. Verify the common velocity

   Watch the two carts stick and read the post-collision velocity. Compare with the prediction $V = \frac{m_1u_1 + m_2u_2}{m_1+m_2} = \frac{5}{5} = 1$ m/s. Repeat with different m₂ and check the formula — P is conserved even though K is not.

3. Compute the lost energy

   Read "K after" and compute $\Delta K = K_{before} - K_{after}$: this is the part turned into heat, sound, and deformation. For $e = 0$ one can show $\Delta K = \frac{1}{2}\frac{m_1m_2}{m_1+m_2}(u_1-u_2)^2$ — the entire kinetic energy of relative motion is lost. Vary u₂ to see $\Delta K$ follow the squared velocity difference.

Simulation

Experiment history

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