15
普通物理/ General Physics Ch1 測量 / Measurement 成功大學物理學系 朱淑君
/ General PhysicsCh1 / Measurement
19-2
Ch 1 Measurement
1-2 Measuring Things/ 1-3 The International System of Units/ 1-4 Changing Units/ 1-5 Length/ 1-6 Time/ 1-7 Mass/
19-3
1-2 Measuring Things ()
(Measurement)
Ex: 3 m = 3 x 1 m (or ) 1 = 453.59237
Ex: speed=length/time
/(base standard or base quantity)
(Exspeed m/sec)
(base quantity):
:)standard( :(unit)
19-4
1-3 The International System of Units ()
(Metric Unit)1971, 14th (basic quantity)
/SI seven basic units
(Derived units)ex: (Watt)
/////
//
32 /kg 1 W1 sm
19-5
(Scientific notation)
EX:
(E: exponent of ten, )
(Prefixes of SI units)10 SI unit
Ex:
19-6
1-4 Changing Units ()
(Chain-link conversion)(conversion factor) 1
Ex:
[] (Order of Magnitude)
Ex
54
4108.7)2(4102.3 A )1( )16.3~10(
4
4
B
19-7
[] (Significant Figures, SF) (Decimal places)Why? ()
()Ex6.4 mm (6.4 0.1mm, 0.1 mm)
Ex: 0.03 SF=1, 10.075 SF=2, 2
20.58 SF=4, 4
Ex:
)0.0002300 (410 300.2)0.00023 (210 2.3
410 500.1210 .51
4-
4-
3
3
SFSF
SFSF
19-8
(Note: , )
2
)3(SF
2
)()3(
3
)6(
22
2)(SF)(
2
)2()2(
133...333.13308.1000.144
)135( 35 2.353.64.5
cmcmcmcm
cmcmcmcmcm
SFSF
SFSF
1 ,004.0998.0002.14 ,004.1003.0001.1
3 , 128 35.12835.12835.5123)(
SFSF
SFcmcmcm
(6.03 X 5.5 6.03 + 5.5 )
19-9
--- ()Why
EX SF=3
Note
0505
)(),0(
286.0286500.0
24.323500.3 )4(
),0( 24.323510.3 )3()( 27.326600.3 )2()( 26.326400.3 )1(
3
3
3
3
3
SF
SF
SF
SF
SF
19-10
1-5 Length ()
(1792)Kr-861650763.73 (1960) 1/299792458 (1983)
(hint: 4mm x 4mm )
1.01
19-11
1-6 Time ()
SI unit, 1 1/86400
(quartz clock)
(Cesium clock)Cs133 9192631770
()
0.03sec
19-12
1-7 Mass ()
1 (The standard kilogram)
(A second mass standard) C12 12 (atomic mass units), 12u
( C12 )
(Density)
Ex 10% (platinum) 21
19-13HW: 4, 9, 13, 22, 25, 28
1.02
Homework
19-14
19-15
