Two balls are moving toward each other! Press **▶ Play** to watch them collide. The setup: - **Red ball:** mass 1 kg, moving right at 3 m/s - **Blue ball:** mass 1 kg, moving left at 3 m/s - **Total momentum:** zero (equal and opposite) After the collision, watch what happens to their velocities. Then ask me: - *"Is this an elastic or inelastic collision?"* - *"What if the red ball were twice as heavy?"* - *"Calculate the kinetic energy before and after"*

3D Collision Simulator

Two balls collide in 3D — momentum conserved, energy revealed

Every collision in physics — billiard balls, car crashes, subatomic particles — follows one unbreakable rule: momentum is conserved. The total momentum before the collision equals the total momentum after. This is a direct consequence of Newton's third law: every force has an equal and opposite reaction.

In this 3D collision simulator, a red ball and a blue ball approach each other with equal and opposite velocities. When they meet, they bounce apart. Depending on whether the collision is elastic (kinetic energy conserved) or inelastic (some energy lost as heat/deformation), the outcome differs:

  • Elastic collision: balls bounce off at the same speeds (billiard balls)
  • Perfectly inelastic: balls stick together after impact (clay balls)
  • Partially inelastic: balls bounce but slower (most real collisions)

Key formula — momentum conservation: m_1 v_1 + m_2 v_2 = m_1 v_1' + m_2 v_2'

Press ▶ Play to watch the collision and ask the AI to calculate final velocities, compare elastic vs inelastic outcomes, or change the ball masses.

Related Topics

3D Projectile MotionInclined Plane Simulator2D VectorsDerivatives
What is momentum conservation?
The total momentum of a closed system (no external forces) never changes. For two objects: m₁v₁ + m₂v₂ = m₁v₁' + m₂v₂'. Momentum is a vector — direction matters. In this simulator, both balls have the same mass and equal-but-opposite velocities, so total momentum is zero before and after.
What is the difference between elastic and inelastic collisions?
In an elastic collision, both momentum AND kinetic energy are conserved — the balls bounce off at the same speeds they approached (like billiard balls or gas molecules). In an inelastic collision, momentum is still conserved, but kinetic energy decreases — some energy converts to heat, sound, or deformation. Most real collisions are partially inelastic.
What is Newton's third law in a collision?
During impact, ball 1 exerts a force on ball 2, and ball 2 exerts an equal and opposite force on ball 1. These forces act for the same duration (the contact time), so the impulse (force × time) is equal and opposite — which is why momentum is transferred from one ball to the other.
What happens when two equal-mass balls collide head-on in an elastic collision?
When two equal-mass balls collide elastically in a head-on collision, they exchange velocities completely. The ball that was moving right stops, and the ball that was moving left stops — they swap speeds exactly. This is the classic result of solving the conservation equations simultaneously.
How do I calculate the final velocities after a collision?
For an elastic collision between mass m₁ (velocity v₁) and m₂ (velocity v₂): v₁' = (m₁−m₂)v₁/(m₁+m₂) + 2m₂v₂/(m₁+m₂) and v₂' = (m₂−m₁)v₂/(m₁+m₂) + 2m₁v₁/(m₁+m₂). For equal masses, these simplify to v₁' = v₂ and v₂' = v₁ — a perfect velocity swap.