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Impulse

Part of the Mechanics section of Coddy's Physics journey. Lesson 63 of 94.

The impulse J is the net force times the time it acts. It equals the change in momentum:

J = F Δt = Δp

Its unit is N·s, the same as kg·m/s.

The same change in momentum can come from a large force over a short time or a small force over a long time: a crash mat makes the stop last longer, so the force is smaller.

Two force against time graphs: a tall rectangle of 800 newtons lasting 0.1 seconds and a low, wide rectangle of 200 newtons lasting 0.4 seconds; both shaded areas are 80 newton seconds

The area under each graph is the impulse: 800 · 0.1 = 200 · 0.4 = 80 N·s.

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Challenge

A 60 kg stunt performer falls onto an air cushion at 8 m/s and is stopped in 0.4 s. Taking up as positive, find the net force F on her while she stops.

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All lessons in Mechanics

1Vectors 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

4Kinematics in 1D

Position and DisplacementVelocityAccelerationMotion GraphsEquations of MotionRecap - Braking Car

7Kinematics and Newton

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

10Springs

Hooke's LawSprings in SeriesSprings in ParallelRecap - Spring Scale

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

Mission BriefingTakeoff ThrustClimb to AltitudeCruise and BrakePackage Drop

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

MomentumImpulseConservation of MomentumElastic CollisionsInelastic CollisionsRecap - Air Track

15Simple Harmonic Motion

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