Collisions Guided Notes
Physics Dynamics Crash Course Series
Name: Date: Period:
CRASH COURSE: COLLISIONS
Interactive Fill-in-the-Blank Notes • Momentum, Impulse & Impact Dynamics
Unit Focus Newtonian Mechanics
1 Linear Momentum: Mass in Motion
\( \vec{p} = m\vec{v} \)
• Momentum (\(p\)) is defined as an object's in motion. It is the product of an object's mass and its .
• Momentum is a quantity, meaning direction matters! Its direction is identical to the vector.
• The standard SI unit for linear momentum is: (or \( \text{N}\cdot\text{s} \)).
Quick Check: A 1,000 kg vehicle moves East at 20 m/s. Its momentum is:
kg·m/s East
2 Impulse & The Impulse-Momentum Theorem
\( \vec{J} = \vec{F}_{\text{net}}\Delta t = \Delta \vec{p} \)
• An (\(J\)) occurs when a net force acts upon an object over an interval of .
• According to the theorem, Impulse equals the in momentum: \( \vec{F}_{\text{net}}\Delta t = m\vec{v}_f - \) .
• On a Force vs. Time graph (\(F \text{ vs. } t\)), the area under the curve represents the .
Hard Barrier (Short \(\Delta t\))
• Impact duration (\(\Delta t\)) is very .
• Peak impact force (\(F_{\text{net}}\)) is extremely .
Cushioned Stop (Long \(\Delta t\))
• Impact duration (\(\Delta t\)) is significantly .
• Peak impact force (\(F_{\text{net}}\)) is greatly .
3 Real-World Physics: Automotive Crash Safety
Engineering Focus
Crumple Zones
Designed to deform, extending the collision to minimize impact force on occupants.
Airbags
Increases stopping time and spreads the impact force over a larger area.
Seatbelts
Slightly stretch to prolong stop duration and keep passengers inside the safe .
Unit 4 • Momentum & Impulse Lecture Guide Page 1 of 2
Crash Course: Collisions Part II: Systems & Conservation
Student Notes & Mastery Check
4 Classifying Collisions: Elastic vs. Inelastic
Kinetic Energy (\(KE\)) vs. Momentum (\(p\))
| Collision Type | Momentum | Kinetic Energy (\(KE\)) | Key Behavior / Example |
|---|
| Elastic | Conserved | Is (no heat/sound) | Objects bounce cleanly; no shape change (e.g. pool balls). |
| Inelastic | Conserved | Is (lost to heat/sound) | Objects bounce apart deformed (e.g. tennis ball on court). |
| Perfect Inelastic | Conserved | \(KE\) is lost | Objects stick and move with shared final . |
5 The Law of Conservation of Momentum
\( \sum \vec{p}_{\text{initial}} = \sum \vec{p}_{\text{final}} \)
• In an system, total momentum before collision equals total momentum collision.
• General Two-Body Formula: \( m_1 v_{1i} + m_2 v_{2i} = \)
• Perfectly Inelastic (Sticking): \( m_1 v_{1i} + m_2 v_{2i} = (m_1 + m_2) \cdot \)
• Explosion / Recoil (\(p_{\text{initial}} = 0\)): \( 0 = m_1 v_1 + \)
6 Comprehension Checks & Crash Exit Ticket
Independent Application
1. Concept Check: Skater A (80 kg) and Skater B (40 kg) push off each other from rest on frictionless ice. Which skater moves away with greater speed, and why?
2. Calculation Check: A 4 kg cart at 6 m/s East collides and sticks to a stationary 2 kg cart.
Show calculation: \( m_1 v_1 = (m_1 + m_2) v_f \) Final Speed (\(v_f\)) = m/s
Exit Ticket: Safety Engineer Challenge Use \( \vec{F}_{\text{net}}\Delta t = m\Delta\vec{v} \)
Why is a head-on collision much more survivable when a car's front end crumples compared to if the car were made of rigid steel that doesn't deform?
Unit 4 • Momentum & Impulse Lecture Guide Page 2 of 2
