Aristotle said the objects’ natural state is at rest.

Which trip will take more fuel?  A trip that requires 300km of driving, or trip that requires 3,000km of driving.

Newton’s First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.

Which space trip would use more fuel.  A trip of 1.5 seconds (Moon) or 182 seconds (Mars close) or 22 minutes (Mars far)

Momentum Conservation: http://phet.colorado.edu/en/simulation/legacy/collision-lab

Field, force at a distance:  http://phet.colorado.edu/en/simulation/legacy/charges-and-fields

Inverse square law: http://phet.colorado.edu/en/simulation/legacy/electric-hockey

What if it is not linear: http://demonstrations.wolfram.com/MotionInACentralField/

http://phet.colorado.edu/en/simulation/legacy/gravity-and-orbits

http://phet.colorado.edu/en/simulation/legacy/my-solar-system

http://phet.colorado.edu/en/simulation/legacy/motion-2d

http://demonstrations.wolfram.com/OrbitOfALaunchedSatellite/

Uniform field and a charge.  Inverse square law: http://phet.colorado.edu/en/simulation/legacy/efield

http://phet.colorado.edu/en/simulation/legacy/gravity-and-orbits

Cross product, dot product.

cross product: http://demonstrations.wolfram.com/CrossProductOfVectors/

Friction:  http://phet.colorado.edu/en/simulation/legacy/the-ramp

Position velocity and acceleration: http://phet.colorado.edu/en/simulation/legacy/moving-man

http://phet.colorado.edu/en/simulation/legacy/motion-2d

http://phet.colorado.edu/en/simulation/legacy/forces-1d

http://phet.colorado.edu/en/simulation/legacy/calculus-grapher

http://phet.colorado.edu/en/simulation/legacy/lunar-lander

Three accelerators in the car.