Position-Time and Velocity-Time Graphs：位置的时间和速度时间曲线图

1、Position-Time and Velocity-Time GraphsQuestions for ConsiderationlWhat is a position-time graph?lWhat is a velocity-time graph?lHow do features on one graph translate into features on the other?Position-Time GraphslShow an objects position as a function of time.lx-axis: timely-axis: positionPosition

2、-Time GraphslImagine a ball rolling along a table, illuminated by a strobe light every second.lYou can plot the balls position as a function of time.0 s1 s2 s3 s4 s5 s6 s7 s8 s9 s 10 sPosition-Time Graphs1234567891012345678910time (s)position (cm)Position-Time GraphslWhat are the characteristics of

3、this graph?lStraight line, upward slopelWhat kind of motion created this graph?lConstant speed1234567891012345678910time (s)position (cm)Position-Time GraphslEach type of motion has a characteristic shape on a P-T graph.lConstant speedlZero speed (at rest)lAccelerating (speeding up)lDecelerating (sl

4、owing down)Position-Time GraphslConstant speed is represented by a straight segment on the P-T graph.time (s)pos. (m)Constant speed in positive direction.time (s)pos. (m)Constant speed in negative direction.Position-Time GraphslConstant speed is represented by a straight segment on the P-T graph.tim

5、e (s)pos. (m)A horizontal segment means the object is at rest.Position-Time GraphslCurved segments on the P-T graph mean the objects speed is changing.time (s)pos. (m)Speeding up in positive direction.time (s)pos. (m)Speeding up in negative direction.Position-Time GraphslCurved segments on the P-T g

6、raph mean the objects speed is changing.time (s)pos. (m)Traveling in positive direction, but slowing down.time (s)pos. (m)Traveling in negative direction, but slowing down.Position-Time GraphslThe slope of a P-T graph is equal to the objects velocity in that segment.time (s)position (m)1020304010203

7、04050slope = change in ychange in xslope = (30 m 10 m)(30 s 0 s)slope = (20 m)(30 s)slope = 0.67 m/sPosition-Time GraphslThe following P-T graph corresponds to an object moving back and forth along a straight path. Can you describe its movement based on the graph?time (s)position (m)NSVelocity-Time

8、GraphslA velocity-time (V-T) graph shows an objects velocity as a function of time.lA horizontal line = constant velocity.lA straight sloped line = constant acceleration.lAcceleration = change in velocity over time.lPositive slope = positive acceleration.lNot necessarily speeding up!lNegative slope

9、= negative acceleration.lNot necessarily slowing down!Velocity-Time GraphslA horizontal line on the V-T graph means constant velocity.time (s)velocity (m/s)NSObject is moving at a constant velocity North.Velocity-Time GraphslA horizontal line on the V-T graph means constant velocity.time (s)velocity

10、 (m/s)NSObject is moving at a constant velocity South.Velocity-Time GraphslIf an object isnt moving, its velocity is zero.time (s)velocity (m/s)NSObject is at restVelocity-Time GraphslIf the V-T line has a positive slope, the object is undergoing acceleration in positive direction.lIf v is positive

11、also, object is speeding up.lIf v is negative, object is slowing down.Velocity-Time GraphslV-T graph has positive slope.time (s)velocity (m/s)NSPositive velocity and positive acceleration: object is speeding up!time (s)velocity (m/s)NSNegative velocity and positive acceleration: object is slowing down.Velocity-Time GraphslIf the V-T line has a negative slope, the object is undergoing acceleration in the negative direction.lIf v is positive, the object is slowing down.lIf v is negative also, the object is speeding up.Velocity-Time GraphslV-T graph has negative slope.time (s)velocity (m