Physics 2 — Momentum & Waves

Collisions — momentum is conserved

continues from lesson 1 — values defined earlier in the course stay live here

When two things collide, the total momentum before equals the total after — no exceptions. If they stick together (a perfectly inelastic collision), one equation gives the final speed:

m_{1} := 1200 kg

= 1200 kg car

v_{i1} := 15 m/s

= 15 m / s

m_{2} := 800 kg

= 800 kg car it rear-ends, initially parked

v_{f} = \frac{m_{1} \cdot v_{i1}}{m_{1} + m_{2}}

= 9 m / s they lock bumpers and move together

✓ pass

abs(m_{1} * v_{i1} - (m_{1} + m_{2}) * v_{f}) < 0.001 kg*m/s

momentum books balance

E_{lost} = \frac{1}{2} \cdot m_{1} \cdot v_{i1}^{2} - \frac{1}{2} \cdot \left(m_{1} + m_{2}\right) \cdot v_{f}^{2}

= 54000 J kinetic energy is NOT conserved — this became crumpled metal and heat