Matter & Motion

Isaac Newton 1643 – 1727 Newton, age 46 Newton, age 82

Motion – Terms & Definitions Speed = rate of change of position e.g., miles/hour, meters/second Velocity = speed in a specific direction e.g., 20 meters/sec, north 20 kilometers/sec, up Acceleration = rate of change of velocity * requires change in speed and/or direction

 Auto goes from 0 to 90 mph in 7 sec: accelerated motion Auto rounds curve at constant 40 mph: accelerated motion

Catch a baseball – ball stops: accelerated motion

Laws of Motion 1. In the absence of a net force, an object moves with constant velocity. * Force = “push or pull”

Laws of Motion In the absence of a net force, an objects tend to maintain constant velocity. 2. For every action force, there exists an equal and opposite reaction force: action = reaction

If gravity exceeds air resistance, then person accelerates. Falling through the atmosphere . . . Net force is combination of air resistance and gravity. air resistance If gravity exceeds air resistance, then person accelerates. gravity

Catching a ball . . . again: FH  Force on hand due to ball FB  Force on ball due to hand FH = FB FH FB

Rocket Propulsion . . . Rocket pushes on exhaust; exhaust pushes on rocket. Forces are equal! Yeah!