PHYSICS I PHY 093PHY 093 - Universiti Teknologi MARAzuhairusnizam.uitm.edu.my/lecture notes/phy093-chapter 1.pdfPHYSICS I PHY 093PHY 093 Zuhairusnizam Md Darus Email: znzam@@ysalam.uitm.edu.my

PHYSICS IPHY 093PHY 093

Zuhairusnizam Md DarusEmail: [email protected]@ y

PhoneOffice : 03 5544 2140Mobile: 012 369 0020Mobile: 012 369 0020

Website: http://zuhairusnizam.uitm.eu.myEmail: [email protected]

UiTM Shah Alam : Unit Percetakan Universiti (UPENA)UiTM Puncak Alam :Aras 4

Physical Quantities and UnitsBase Quantities and SI UnitsSignificant FiguresConversion of UnitsDimensional AnalysisScalars and Vectors

1, 2

Ch 1 3 7

Laws of ThermodynHeat Capacity of Gases

RECOMMENDED TEXT:PHYSICS For Scientists & Engineers With Modern Physics by Giancoli, 4th Edition

REFERENCES:Fundamental of Physics by Halliday, Resnick, W lk 6th 7th Ed J h Wil &S I

15

Mechanics of MotionMotion with Constant Acceleration (1 – D)

Scalars and VectorsCh 1, 3, 7

Gases and Kinetic Theory

p yWork and Internal EnergyFirst Law of ThermodynamicsSecond Law of Thermodynamics

Walker;6th or 7th Ed., John Wiley &Sons, Inc.

ASSESSMENT:TESTS – 30%LAB REPORTS – 10%FINAL EXAM – 60 %

3

Ch 2

Ch 19, 20

093

Mechanics of MotionMotion with Constant Acceleration (2 – D)

Newton’s Laws and ApplicationsCircular MotionTemperature and Heat

T d Th l E

Gases and Kinetic TheoryGas Laws and Absolute TempKinetic Theory of Gases

4

Ch 3

513

14

Ch 18

093 C cu a ot oUniform Circular MotionCentripetal and Angular AccnCentripetal Force

States of Matter

Temp and Thermal EqmThermometers and Temp ScaleThermal Expansion of Solids n LiquidsHeat

Ch 4, 5

612

Ch 17

Work and EnergyWork by a Varying ForceKE n W-KE TheoremPE Conservation of Energy

States of MatterSolid – Stress & StrainYoung’s ModulusFluids – Density and PressureArchimedes’ PrincipleBernoulli’s Principle

6

Ch 7, 8

11

Ch 12, 13

Momentum, Impulse and Collissions

Rotational MotionRotational DynamicsAngular Momentum

GravitationNewton’s Law of GravitationGravitational Field StrengthGravitational PotentialRealtionship bet g and GSatellite Motion in Cicular OrbitsEscape velocity

7

Ch 9

8

9

Ch 10, 11

10

Ch 6

B R E A K

(18/7 – 25/7)StaticsEquilibrium of ParticlesFree-body diagramEquilibrium of Rigid Bodies

Ch 12

Prepared by Prof Madya Ahmad Abd Hamid, May 2010

Zuhairusnizam Md DarusPhoe: 0123690020 Off : 03 5544 2140Unit Penerbitan Universiti (UPENA)http://zuhairusnizam.uitm.edu.myEmail:[email protected]

LECTURESLECTURES

Units of Chapter 1Th N t f S i• The Nature of Science

• Models, Theories, and Laws

• Measurement and Uncertainty; Significant Figuresy; g g

• Units, Standards, and the SI System

• Converting Units

• Order of Magnitude: Rapid Estimating

• Dimensions and Dimensional Analysis

Copyright © 2009 Pearson Education, Inc.

1-1 The Nature of Science

Observation: important first step toward scientific theory; requires imaginationto tell what is important

Th i t d t l i b ti ill k di tiTheories: created to explain observations; will make predictions

Observations will tell if the prediction is accurate, and the cycle goes on.

No theory can be absolutely verified, although a theory can be proven false.y y , g y p


1-1 The Nature of ScienceHow does a new theory get accepted?How does a new theory get accepted?

• Predictions agree better with data

• Explains a greater range of phenomena

Example: Aristotle believed that objects would return to a state of rest once put in motion.

Galileo realized that an object put in motion would stay in motion until someGalileo realized that an object put in motion would stay in motion until some force stopped it.


1-1 The Nature of Science

The principles of physics are used in many practical applications, including p p p y y p pp , gconstruction. Communication between architects and engineers is essential if disaster is to be avoided.


1-2 Models, Theories, and LawsModels are very useful during the process of understanding phenomena. A model creates mental pictures; care must be taken to understand the limits of the model and not take it too seriously.

A theory is detailed and can give testable predictions.

A law is a brief description of how nature behaves in a broad set of circumstances.

A principle is similar to a law but applies to a narrower range of phenomenaA principle is similar to a law, but applies to a narrower range of phenomena.


1-3 Measurement and Uncertainty; Significant FiguresFigures

No measurement is exact; there is always some uncertainty due to limited instrument accuracy and difficulty reading results.

The photograph to the left illustrates this – it would be difficult to measure the width of this board more accurately than ± 1 mm± 1 mm.



E ti t d t i t i itt ith i f l 8 8 0 1Estimated uncertainty is written with a ± sign; for example: 8.8 ± 0.1 cm.

Percent uncertainty is the ratio of the uncertainty to the measured value, multiplied by 100:



The number of significant figures is the number of reliably known digits in a number. It is usually possible to tell the number of significant figures by the way the number is y p g g y ywritten:

23.21 cm has four significant figures.

0 062 cm has two significant figures (the initial zeroes don’t count)0.062 cm has two significant figures (the initial zeroes don t count).

80 km is ambiguous—it could have one or two significant figures. If it has three, it should be written 80.0 km.



When multiplying or dividing numbers, the result has as many significant figures as the number used in the calculation with the fewest significant figures.

Example: 11.3 cm x 6.8 cm = 77 cm.

When adding or subtracting, the answer is no more accurate than the leastaccurate number used.accu a e u be used

The number of significant figures may be off by one; use the percentageuncertainty as a check.



Calculators will not give you the right number of significant figures; they usually give too many but sometimes give too fewfigures; they usually give too many but sometimes give too few(especially if there are trailing zeroes after a decimal point).

The top calculator shows the result of 2.0/3.0.

The bottom calculator shows the result of 2.5 x 3.2.



Conceptual Example 1-1: Significant figures.

Using a protractor, you measure an angle to be 30°. (a) How many significant figures should you quote in this measurement? (b) Use a calculator to find thethis measurement? (b) Use a calculator to find the cosine of the angle you measured.



Scientific notation is commonly used in physics; it allows the number of significant figures to be clearly shownsignificant figures to be clearly shown.

For example, we cannot tell how many significant figures the number 36,900 has. However, if we write 3.69 x 104, we know it has three; if we write 3.690 x 104 it has four104, it has four.

Much of physics involves approximations; these can affect the precision of a measurement also.



Accuracy vs. Precision

Accuracy is how close a measurement comes to the true value.

Precision is the repeatability of the measurement using the same instrument.

It is possible to be accurate without being precise and to be precise withoutIt is possible to be accurate without being precise and to be precise without being accurate!


1-4 Units, Standards, and the SI SystemQ i U i S d dQuantity Unit StandardLength Meter Length of the path traveled

by light in 1/299,792,458 second

Ti S d Ti i d fTime Second Time required for 9,192,631,770 periods of radiation emitted by cesiumradiation emitted by cesium atoms

Mass Kilogram Platinum cylinder inMass Kilogram Platinum cylinder in International Bureau of Weights and Measures, Paris


g ,

1-4 Units, Standards, and the SI System






1-4 Units, Standards, and the SI SystemSI System

These are the standard SI prefixes for indicating powers of 10. Many are familiar; yotta, zetta, exa, hecto, deka, atto, zepto,yotta, zetta, exa, hecto, deka, atto, zepto, and yocto are rarely used.


1-4 Units, Standards, and the SI SystemWe will be working in the SI system in which the basicWe will be working in the SI system, in which the basic units are kilograms, meters, and seconds. Quantities not in the table are derived quantities, expressed in terms of q , pthe base units.

Other systems: cgs; units are y gcentimeters, grams, and seconds.

British engineering system hasBritish engineering system has force instead of mass as one of its basic quantities, which are q ,feet, pounds, and seconds.


1-5 Converting UnitsUnit conversions always involve a conversion factor.

Example: 1 in. = 2.54 cm.

Written another way: 1 = 2 54 cm/inWritten another way: 1 = 2.54 cm/in.

So if we have measured a length of 21.5 inches, and wish to convert it to centimeters, we use the conversion factor:


1-5 Converting UnitsE l 1 2 Th 8000 kExample 1-2: The 8000-m peaks.

The fourteen tallest peaks in the world are referred to as “eight-thousanders,” meaning their summits are over 8000 m above sea level. What is the elevation, in feet of an elevation of 8000 m?in feet, of an elevation of 8000 m?


1-6 Order of Magnitude: Rapid Estimating

A quick way to estimate a calculated quantity is to round off all numbers to one significant figure and then calculate Your result should at least be theone significant figure and then calculate. Your result should at least be the right order of magnitude; this can be expressed by rounding it off to the nearest power of 10.

Diagrams are also very useful in making estimations.


1-6 Order of Magnitude: Rapid EstimatingExample 1-5: Volume of a lake.

Estimate how much water there is in a particular lake, which is roughly circular, about 1 km across, and you guess it has an average depth of about 10 man average depth of about 10 m.


1-6 Order of Magnitude: Rapid EstimatingExample 1-6: Thickness of a page.

Estimate the thickness of a page of your te tbook (Hint o don’t need one oftextbook. (Hint: you don’t need one of these!)


1-6 Order of Magnitude: Rapid EstimatingExample 1-7: Height by triangulation.

Estimate the height of the building shown by “triangulation,” with the help y g , pof a bus-stop pole and a friend. (See how useful the diagram is!)


1-6 Order of Magnitude: Rapid Estimating

Example 1-8: Estimating the radius of Earth.

If you have ever been on the shore of a large lake, you may have noticed that you cannot see the beaches, piers, or rocks at water level across the lake on the opposite shore The lakeacross the lake on the opposite shore. The lake seems to bulge out between you and the opposite shore—a good clue that the Earth is ro nd S ppose o climb a stepladder andround. Suppose you climb a stepladder and discover that when your eyes are 10 ft (3.0 m) above the water, you can just see the rocks at water level on the opposite shore. From a map, you estimate the distance to the opposite shore as d ≈ 6.1 km. Use h = 3.0 m to estimate the


as d 6.1 km. Use h 3.0 m to estimate the radius R of the Earth.

1-7 Dimensions and Dimensional AnalysisDi i f tit th b it th t k it th llDimensions of a quantity are the base units that make it up; they are generally written using square brackets.

Example: Speed = distance/time

Dimensions of speed: [L/T]

Quantities that are being added or subtracted must have the same dimensions. In addition, a quantity calculated as the solution to a problem yshould have the correct dimensions.


1-7 Dimensions and Dimensional AnalysisDimensional analysis is the checking of dimensions of all quantities in an equation to ensure that those which are added, subtracted, or equated have the same dimensions.

Example: Is this the correct equation for velocity?

Check the dimensions:


Wrong!

Summary of Chapter 1• Theories are created to explain observations and then tested based on theirTheories are created to explain observations, and then tested based on their predictions.

• A model is like an analogy; it is not intended to be a true picture, but to provide a familiar way of envisioning a quantityfamiliar way of envisioning a quantity.

• A theory is much more well developed, and can make testable predictions; a law is a theory that can be explained simply, and that is widely applicable.

Di i l l i i f l f h ki l l ti• Dimensional analysis is useful for checking calculations.


Summary of Chapter 1M t b t th i l t i t It i• Measurements can never be exact; there is always some uncertainty. It is

important to write them, as well as other quantities, with the correct number of significant figures.

• The most common system of units in the world is the SI system• The most common system of units in the world is the SI system.

• When converting units, check dimensions to see that the conversion has been done properly.

• Order-of-magnitude estimates can be very helpful.


Chapter 3p

Chapter 3

Vectors

3-1 Vectors and Scalars

A vector has magnitude as well as direction.

Some vector quantities: displacement, velocity, force, momentum

A scalar has only a magnitude.

Some scalar quantities: mass, time, temperature

3-2 Addition of Vectors—Graphical Methods

For vectors in one dimension, simple addition and subtraction are all that isaddition and subtraction are all that is needed.

You do need to be careful about the signs, as the figure indicatesas the figure indicates.

3-2 Addition of Vectors—Graphical MethodsIf the motion is in two dimensions, the situation is somewhat more complicated.

Here, the actual travel paths are at right angles to one another; we can find the displacement by using the Pythagorean Theorem.

3-2 Addition of Vectors—Graphical MethodsAdding the vectors in the opposite order gives the same result:g pp g

3-2 Addition of Vectors—Graphical MethodsE if th t t t i ht l th b dd dEven if the vectors are not at right angles, they can be added graphically by using the tail-to-tip method.

3-2 Addition of Vectors—Graphical MethodsThe parallelogram method may also be used; here again the vectors must be tail-p g y ; gto-tip.

3-3 Subtraction of Vectors, and Multiplication of a Vector by a Scalarp y

In order to subtract vectors, we define the negative of a vector, which has the same magnitude but points in the oppositeg p ppdirection.

Then we add the negative vector.

3-3 Subtraction of Vectors, and Multiplication of a Vector by a Scalarp y

A vector can be multiplied by a scalar c; the result is a vector cthat has the same direction but a magnitude cV. If c is negative, the

rV r

Vg g

resultant vector points in the opposite direction.V

3-4 Adding Vectors by Components

Any vector can be expressed as the sum of two other vectors, which are called its components. Usually the other vectors are chosen so that they are perpendicular to each other.they are perpendicular to each other.


If the components are perpendicular, they can be found using trigonometric functions.


The components are effectively one-dimensional, so they can be added arithmetically.


Adding vectors:

1. Draw a diagram; add the vectors graphically.

2. Choose x and y axes.

3. Resolve each vector into x and y components.

4. Calculate each component using sines and cosines.

5. Add the components in each direction.p

6. To find the length and direction of the vector, use:

and .

3-4 Adding Vectors by Componentsp

Example 3-2: Mail carrier’s displacement.

A rural mail carrier leaves the post office and drives 22.0 km in a northerly direction. She then drives in a direction 60.0° south of east for 47.0 km. What is her displacement from the post office?displacement from the post office?

3-4 Adding Vectors by Componentsp

Example 3-3: Three short trips.

An airplane trip involves three legs, with two stopovers. The first leg is due east for 620 km; the second leg is southeast (45°) for 440 km; and the third leg is at 53° south of west, for 550 km, asthird leg is at 53 south of west, for 550 km, as shown. What is the plane’s total displacement?

3-5 Unit Vectors3 5 Unit VectorsUnit vectors have magnitude 1.

Using unit vectors, any vector rcan be written in terms of its components: V

3-6 Vector Kinematics

In two or three dimensions, the displacement is a vector:

3-6 Vector KinematicsAs ∆t and ∆r become smaller and smaller, the average velocity approaches the instantaneous velocity.

7-2 Scalar Product of Two VectorsDefinition of the scalar or dot product:Definition of the scalar, or dot, product:

Therefore, we can write:

7-2 Scalar Product of Two VectorsE l 7 4 U i th d t d tExample 7-4: Using the dot product.

The force shown has magnitude FP = 20 N and makes an angle of 30° to the ground. Calculate the work done by this force, using the dot product, when the wagon is dragged 100 m along the groundwagon is dragged 100 m along the ground.

11-2 Vector Cross Product; Torque as a VectorTorque as a Vector

The vector cross product is defined as:

The direction of the cross product is defined by a right-hand rule:


The cross product can also be written in determinant form:


Some properties of the cross product:


Torque can be defined as the vector product of the force and the vector from the point of action of the force to the axis of rotation:p


For a particle, the torque can be defined around a point O:

Here, is the position vector from the particle relative to O.rr

11‐2 Vector Cross Product; Torque as a Vector

Example 11-6: Torque vector.

Suppose the vector is in the xz plane, and is given by

as a Vectorrr

= (1.2 m) + (1.2 m)

Calculate the torque vector if = (150 N) .rτ

rr

Fr

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PHYSICS I PHY 093PHY 093 - Universiti Teknologi MARAzuhairusnizam.uitm.edu.my/lecture notes/phy093-chapter 1.pdfPHYSICS I PHY 093PHY 093 Zuhairusnizam Md Darus Email: znzam@@ysalam.uitm.edu.my