SpeedAPRIL11TH, 2018
Objective
◦Iwillbeabletoanalyzegraphsandunderstand
therelationshipbetweendistance,time,and
speed
Speed,v◦Thedistance anobjectmovesinacertainlengthoftime
Speedisa quantity
Representedbyanumberandunits(i.e.km/h,m/s,cm/s)SIunit:metres/second(m/s)
Constantspeed:
Changingspeed:
Constantspeed:
Changingspeed:
◦Whenanobjecttravelsthesamedistanceforeachtimeinterval
Constantspeed:
Changingspeed:
◦Whenanobjecttravelsthesamedistanceforeachtimeinterval
Whenanobjecttravelsadifferentdistanceforeachtimeinterval
Graphingdistance,time,andspeed
Distance-timegraph
Distance-TimeGraph
Slope=m =!"#$!%&
='(')
'(')
='?'?
Distance-TimeGraph
Slope=m =!"#$!%&
='(')
'(')
='+',
=?
Use the slope to calculate average speed!
Slope=m =!"#$!%&
='(')
'(')
='+',
=vavg
Averagespeed◦Thedistancetravelledbyanobjectisdividedbythetimeittakestotravelthatdistance
𝑣avg = '+',
Averagespeed=+"#,0&1$,!02$33$+,4,03,"5$$306#$+
Example
◦Determinetheaveragespeedoftheobjectfrom4.5sto7.5s.
m =!"#$!%&
='(')
=(78(")78)"
= 88
=________m/s
Lookatonepoint(instant)onthegraph
Whatistheslope(speed)atthatpoint?
Thisiscalled…
Instantaneousspeed
◦Thespeedataspecificinstant oftime
◦Useaverysmalltimeinterval
Whenthespeedisconstant…
Whatdoyounoticeabouttherelationshipbetweenvinst andvavg?
Whenthespeedisconstant…
vinst isequal tovavgforthattime
interval
vinst = vavg
Homework◦Reading◦P.220-223
◦Questions:Showyourwork!◦Yesterday:P.219#5-7,11,18◦Speed:P.219#9,15-16
CommentaryActivity
1. Designaracebetweentwo
runners
2. Plotadistance-time graph
3. Writeacommentary
4. Tomorrow:Actouttheskit