Center of Mass & Momentum in 2D – AP Physics C | ShowMeClass

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Center of Mass & Momentum in 2D

AP Physics C · Unit 4: Momentum

Learning Objectives

Calculate center of mass for a system of particles

Apply conservation of momentum in 2D collisions

Analyze CM motion: v_cm = p_total / M_total

Distinguish elastic vs inelastic collisions

Key Equations

Legend

Mass 1

Mass 2

Center of Mass

Velocity vectors

Momentum vectors

Collision Types

Elastic: KE conserved. Both objects bounce.

Inelastic: KE not fully conserved. Objects may stick (perfectly inelastic).

In both cases, total momentum is conserved.

Center of MassMomentumCollisions 2DAP Physics C

t =—

x_cm =—

v_cm =—

p_total =—

KE =—

Collision Type

Mass 1 (blue)

m₁ (kg) 3

v₁x (m/s) 4

v₁y (m/s) 1

Mass 2 (red)

m₂ (kg) 2

v₂x (m/s) -3

v₂y (m/s) -1

Speed 1×

Display

Momentum Analysis

📝 Quick Quiz▼

1. In any collision, which quantity is always conserved?

Kinetic energy Total momentum Speed Force

2. The center of mass velocity of an isolated system:

Changes during collision Is always zero Remains constant Doubles after collision

3. In a perfectly inelastic collision, the objects:

Bounce elastically Stick together Both stop Exchange velocities