Chapter 12 Motion

12-1 Frames of Reference *Frame of Reference: object or point from which movement is determined (**the earth) -movement can be measured only with reference to something that is assumed to be fixed in place

12-2 Speed and Velocity video #29 (speed, vel, accel) *Motion: change in position relative to a frame of refer

*Speed: distance / time -dist. in meters or km -time in sec or hr

-constant speed: speed doesn’t change ~graph(slope is directly related to the speed) -aver speed: speed does change ~graph

*Velocity: speed in a given direction

How far did A go before it met B? How long had they been traveling before they met? How far did both travel at the same speed? How long did it take both to get to the end? Which had constant speed? What was their speed(s)?

12-3 Acceleration *Accel: rate of change in vel. = final vel – original vel time

-measured in meters per sec per sec *Deceleration: negative acceleration

-graphing acceleration -distance-time graph for accel is always a curve

-circular motion video #35(centri force-cool sci) -an object in circular motion is accel even though its speed may be constant *Centripetal accel: accel is directed toward the center of a circular path.

12-4 Momentum video #32(22 running with momen) mass multiplied by its velocity -depends on both its mass and velocity

-conservation of momentum *Law of conservation of momentum: total momentum of any group of objects remains the same unless outside forces act on the objects Video #33 (espn sounds of summer)

Practice Problems http://www.ducksters.com/questions/physicsvelocity.php