c3 time, rate and speed

8/19/2019 C3 Time, Rate and Speed

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Time, Rate and

Speed


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3.1 Measuring Time

• Time is the duration of an event.

• Olden methods give inaccurate

measurements of time.• However, man has now developed more

accurate ways of measuring time.


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Units of time

• S.I. unit of time is the second, and

represented by the symbol s.

•Other units of time: minute min!, hour h!,millisecond ms!

• "ime can also be e#pressed in terms of

days, wee$s, months and years.


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Instruments to measure time

• "o measure a short period of time

accurately, we use a stopwatch.

•"here are two types: mechanical andelectronic.


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• %echanical stopwatcho "he mechanical

stopwatch has a minute

scale and a second scale.o "he smallest division on

the mechanical stopwatchis &.' s.

o "hus, the mechanicalstopwatch is accurate to&.' s.

( mechanical stopwatch


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• %echanical stopwatch1. )ress the

operating button to

start the stopwatch.

)ress the operating

button again to stop

the timing.

2. )ress this

button to reset

the stopwatch.

"he minute scale

"he second scale

"he second hand

indicates '*.+ s

"he minute hand falls

on the white area

between & and ' min

of the minute scale."his shows that the

second hand should

be read using the

second scale

between & and *& s.


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• lectronic stopwatch

o "he electronic stopwatch is

more accurate than the

mechanical stopwatch.

o It can measure time intervals

accurate to &.&' s.

o It can also record the timeinterval in hours, unli$e the

mechanical stopwatch.


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• lectronic stopwatch 1. )ress the -StartStop/button to start the stopwatch.

)ress the button again to

stop the timing.2. )ress this

button to reset

the stopwatch.

SecondsHours

%inutes


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3.2 What is Rate?

• ( rate is an e#pression of how one

0uantity changes with time.

• 1ates are useful for ma$ing fair

comparisons.

• )hone charges, internet access plans,

ban$ loan interest rates and inflation rate

are some e#amples of rates in real life.


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3.3 Speed

• Speed is the rate atwhich distance iscovered over time.

• Average speed isused to simplifycalculations since

speed may vary overthe duration of a 2ourney.


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3.3 Speed

• Average speed is the rate at

which total distance travelled

varies with the total time

ta$en.

• (verage speed 3 "otal distance"otal time


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3.3 Speed

• S.I. unit of speed is metre per second

(m/s.

• Other common units of speed: centimetre

per second cms! and $ilometre per hour

$mh!.


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Misce!!aneous

• http:en.wi$ipedia.orgwi$i"ime

• http:en.wi$ipedia.orgwi$i1ate

• http:en.wi$ipedia.orgwi$iSpeed• http:www.timeanddate.com

• http:www.nccc.gov.sgfueleconomyIntrod

uction.shtm• http:www.singstat.gov.sgstats$eyind.ht

ml

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