Menu
CoddyPhysics
Start learning

Inelastic Collisions

Part of the Mechanics section of Coddy's Physics journey. Lesson 69 of 97.

In an inelastic collision some kinetic energy is lost, but momentum is conserved. Bodies that stick together share one velocity:

m1v1+m2v2=(m1+m2) v′m_1 v_1 + m_2 v_2 = (m_1 + m_2)\, v'

In the picture: 2 · 6 = 3v', so v' = 4 m/s4\ \mathrm{m/s}. The kinetic energy drops from 36 J36\ \mathrm{J} to 24 J24\ \mathrm{J}.

Before: a 2 kilogram cart at 6 metres per second moves right toward a 1 kilogram cart at rest. After: the two carts are locked together and move right as one at 4 metres per second

Perfectly inelastic: the carts stick and share one velocity.

challenge icon

Challenge

A 3 kg3\ \mathrm{kg} cart rolls right at 4 m/s4\ \mathrm{m/s}, and a 1 kg1\ \mathrm{kg} cart rolls left at 2 m/s2\ \mathrm{m/s} toward it. They meet and stick together. Taking right as positive, find their velocity vf\relax v_{f} after the collision.

Try it yourself

Physics diagram: cart; arrows v 1 = 4 m/s, v 2 = −2 m/s, v f = ?

Solve for vfv_{f}

quiz iconTest yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Mechanics

1Introduction

What is Physics?Your First EquationTurning a Rule Around

4Inclined Planes

Forces on an InclineGravity ComponentsFrictionless InclineIncline with FrictionWill It Slide?Recap - Ramp Challenge

7Projectile Motion

Independent AxesHorizontal LaunchLaunch at an AngleRange and Max HeightRecap - Hit the Target

10Work and Energy

WorkKinetic EnergyWork-Energy TheoremGravitational PEConservation of EnergyPowerRecap - Roller Coaster

13Impulse and Momentum

MomentumImpulseConservation of MomentumElastic CollisionsInelastic CollisionsRecap - Air Track

16Simple Harmonic Motion

What is SHM?Mass on a SpringThe PendulumSHM GraphsEnergy in SHMRecap - Oscillator

2Vectors and Newton's Laws

Right TrianglesWhat is a Vector?Adding VectorsAxes and DirectionsVector ComponentsForces Around UsFriction and TensionNewton's First LawNewton's Second LawNewton's Third LawRecap - Net Force

5Kinematics in 1D

Position and DisplacementVelocityAccelerationMotion GraphsEquations of MotionRecap - Braking Car

8Kinematics and Newton

From Forces to MotionFrom Motion to ForcesTwo-Stage MotionRecap - Elevator

11Springs

Hooke's LawSprings in SeriesSprings in ParallelRecap - Spring Scale

14Momentum in 2D

Momentum as a Vector2D CollisionsExplosionsRecap - Billiards

17Gravitation

Law of GravitationGravity and AltitudeSatellitesKepler's LawsGravitational EnergyEscape VelocitySatellite EnergyRecap - Mission to Orbit

3Friction

What is Friction?Static FrictionKinetic FrictionFriction and Newton's LawsRecap - Sliding Crate

6Vertical Motion

Free FallThrowing UpwardTime in the AirRecap - Dropped Ball

9Project: Delivery Drone

Mission BriefingTakeoff ThrustClimb to AltitudeCruise and BrakePackage Drop

12Elastic Energy

Elastic Potential EnergySpring LaunchersEnergy with SpringsRecap - Spring Launcher

15Circular Motion

Uniform Circular MotionCentripetal AccelerationHorizontal CirclesVertical CirclesLoop the LoopRecap - Car on a Curve

18Final Challenges

Recap - Stunt RampRecap - Crash TestRecap - Space Probe