Lesson_Text_1.1 - 1 Lesson 1.1 1. Units and Unit Conversion...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Lesson 1.1 1. Units and Unit Conversion Physical quantities are identified by their magnitudes and units. The unit of a physical quantity identifies the type of quantity that is measured. In this course we will be using SI system of units. In this system: The unit of length is the meter (m) The unit of mass is the kilogram (kg) The unit of time is the second (s) The units of many other physical quantities are obtained by combining the units of length, mass and time. For this reason, the units of length, mass and time are called the fundamental units . Units obtained from fundamental units are called derived units . For example: The unit of area is the m 2 . The unit of volume is the m 3 When solving problems, all units must be converted to SI. If length is measured in centimeter (cm), it must be converted to m; if mass is measured in gram (g), it must be converted to kg. 1 m = 10 3 mm 1 m = 10 2 cm 1 m = 10 6 μ m 1 m = 10 9 nm 1 m 2 = 10 4 cm 2 1 m 3 = 10 6 cm 3 1 km = 10 3 m 1 Mm = 10 6 m 1 kg = 10 3 g 1 min = 60 s 1 hr = 3600 s 1 mm = 10 -3 m 1 cm = 10 -2 m 1 μ m = 10 -6 m 1 nm = 10 -9 m 1 cm 2 = 10 -4 m 2 1 cm 3 = 10 -6 m 3 1 g = 10 -3 kg Example 1 : Convert:
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 km m 25 to hr s Solution : 3 1 25 10 25 6.94 6.94 . 3600 km m m m s hr s s - = = = Example 2 : Convert 2.2 cm 2 to m 2 . Solution : 2.2 cm 2 = 2.2 10 -4 m 2 = 2.2 x 10 -4 m 2 Example 3 : Convert 66 mm 3 to m 3 Solution: 66 mm 3 = 66 10 -9 m 3 = 6.6 x 10 -8 m 3 Example 4: The wavelength of red light is 625 nm. Write this in m. Solution : 625 nm = 625 10 -9 m = 6.25 x 10 -7 m Example 5 : Express: 3 3 g kg 3.5 in cm m Solution : 3 3 3 3 6 3 3.5 10 3.5 3.5 10 . 10 kg g cm kg m m - - - - = = × Example 6 : A wire has a diameter 0.5 cm and a length 12 cm. Compute the volume of this wire in m 3 .
Background image of page 2
3 Solution : A wire is a right circular cylinder and its volume is given by 2 V r l π = where r is its radius and l, its length. Here m x cm cm d r 2 10 25 . 0 25 . 0 2 5 . 0 2 - = = = = and l = 12 cm = 0.12 m. Therefore, ( 29 2 2 6 2 0.25 10 0.12 2.4 10 V m - - = × = × Example 7 : The radius of the earth is 6700 km. Find the volume of the earth and express it in m 3 . Solution : Earth is spherical and the volume of a sphere is given by: 3 4 3 V r = Here r = 6700 km = 6700 10 3 m = 6.7 x 10 6 m. Therefore, the volume of the earth is: ( 29 3 6 21 3 4 6.7 10 1.26 10 3 V m = × = × 2. Significant figures. Measured physical quantities are always approximate and cannot be expressed in exact numbers. Measurement always involves a level of uncertainty and we use significant figures to deal with this uncertainty. Significant figures
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 19

Lesson_Text_1.1 - 1 Lesson 1.1 1. Units and Unit Conversion...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online