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Elastic Collisions

Part of the Mechanics section of Coddy's Physics journey. Lesson 65 of 94.

In an elastic collision no kinetic energy is lost. Momentum and the total kinetic energy are both conserved:

½m1 v1² + ½m2 v2² = ½m1 v1'² + ½m2 v2'²

In the picture: 18 J before, 2 + 16 = 18 J after.

Before: a 1 kilogram cart at 6 metres per second moves right toward a 2 kilogram cart at rest. After: the 1 kilogram cart bounces back to the left at 2 metres per second and the 2 kilogram cart moves right at 4 metres per second

An elastic bounce: the light cart comes back, the heavy one moves off.

Equal masses, one at rest: the moving one stops and the other takes its velocity.

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Challenge

A 2 kg glider at 6 m/s hits a second glider at rest on an air track, and the collision is elastic. Afterwards the 2 kg glider keeps going the same way at 2 m/s. Find the kinetic energy K_2 of the second glider.

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All lessons in Mechanics

1Vectors and Newton's Laws

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4Kinematics in 1D

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7Kinematics and Newton

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

10Springs

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13Momentum in 2D

Momentum as a Vector2D CollisionsExplosionsRecap - Billiards

16Gravitation

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

2Friction

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

5Vertical Motion

Free FallThrowing UpwardTime in the AirRecap - Dropped Ball

8Project: Delivery Drone

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11Elastic Energy

Elastic Potential EnergySpring LaunchersEnergy with SpringsRecap - Spring Launcher

14Circular Motion

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

17Final Challenges

Recap - Stunt RampRecap - Crash TestRecap - Space Probe

3Inclined Planes

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

6Projectile Motion

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

9Work and Energy

WorkKinetic EnergyWork-Energy TheoremGravitational PEConservation of EnergyPowerRecap - Roller Coaster

12Impulse and Momentum

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15Simple Harmonic Motion

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