Transcript C1-part 4_5
Welcome to PHY 183 Physics for Scientists and Engineers Meaning of the picture ? PHY 183 Lecturer: MSc: Dương Hiếu Đẩu Vice Dean of COS Head of Physics Dept Email: [email protected] Tel: 84.71. 832061 PHY 183 - Program Physics for Scientists and Engineers Chapter 1 KINEMATICS 7/5 Chapter 2 DYNAMICS 7/5 Chapter 3 WORK AND ENERGY 6/4 Chapter 4 ROTATIONAL MOTION 6/4 The first test 40% (2) Chapter 5 PERIODIC MOTION 5/3 Chapter 6 WAVE MOTION 5/3 Chapter 7 FLUIDS AND THERMAL PHYSICS 5/3 Chapter 8 GAS LAWS AND KINETIC THEORY 5/3 Chapter 9 LIQUID PHASE 6/4 The final examination 60% 1- ELEMENTARY MECHANICS &THERMODYNAMICS John W. Norbury 2- Cơ Nhiệt - Đại cương Nguyễn Thành Vấn & Dương Hiếu Đẩu 3- Fundamentals of Physics (Fourth edition) David Halliday, Robert Resnick, Jearl Walker 4- Principles of Physics Frank J. Blatt Download books and communications 1. Lecturing. 25 H 2. Doing exercises. 18 H 3. Reading books and group discussions. 10 H 1. Seminars. 05 H 2. Testing. 02 H You are free to ask the teacher for your understanding 1. Measurements & units 2. Scalars & vectors 3. Displacement, Velocity and acceleration 4. Relative velocity. 5. Motion in two dimensions and in three dimensions 6. Special case: Gravity Part 1 Measurements Units of Measurement Express this experiment ? Measurement You are making a measurement when you Check your weight * Check your height Read your watch * Take your temperature Looking your face from a mirror Listening to your voice What kinds of measurements did you make today? Standards of Measurement When we measure, we use a measuring tool to compare some dimension of an object to a standard. EX: Use a ruler determine three dimensions of a house Which one can be used for house? Some Tools for Measurement Thermometer Measuring cup, Graduated cylinder Watch Scale Give the names for these tools Learning Check From the previous slide, state the tool (s) you would use to measure thermometer A. temperature ____________________ measuring cup, B. volume ____________________ graduated cylinder ____________________ watch C. time ____________________ scale D. weight ____________________ Measurement in Physics In Physics we do experiments measure quantities use numbers to report measurements Learning Check What are some international units that are used to measure each of the following? A. length B. volume C. weight D. temperature Solution Some possible answers are A. length inch, foot, yard, mile B. volume teaspoon, gallon (4,54L England3,78L US), pint (0.58 L), quart(1.14 L) C. weight ounce, pound (lb), ton D. temperature °F °K °R Metric System (SI) System of international measurements • • • Is a decimal system based on 10 Used in most of the world Used by scientists and hospitals What are fundamental scientific SI unit ? Stating a Measurement In every measurement there is a Number followed by a Unit from measuring device EX: Use a microscope to determine the size of a virus (5 m) Learning Check What is the unit of measurement in each of the following examples? A. The patient’s temperature is 102°F. B. The sack holds 2 Ibs of potatoes. C. It is 8 miles from your house to school. D. The bottle holds 2 L of orange soda. Solution A. °F (degrees Fahrenheit) B. lbs (pounds) C. miles D. L (liters) Learning Check Identify the measurement in metric units. A. John’s height is 1) 1.5 yards 2) 6 feet 3) 2 meters B. The volume of two bottles is 1) 1 liters 2) 1 quart 3) 2 pints C. The mass of a lemon is 1) 12 ounces 2) 145 grams 3) 0.6 pounds Solution A. John’s height is 3) 2 meters B. The volume of two bottles is 1) 1 liter C. The mass of a lemon is 2) 145 grams Learn by heart Name Volume symbol =m Name symbol =m Learn by heart Name =Kg Name X 0C= (X+273) 0K = (0,8X) 0R = = (1,8X+32) 0F =Kg Learning Check Your temperature is 40 0C, it equals to.. A. 314 0K B. 32 0R C. 104 0F D. All are the same System based on 10 Scientific Notation Learning Check Part 2 Vectors and scales Learning Check The sum of two vector A and B (see figure) is C… A =5cm B =5cm C =7.07cm Multiplication of vectors • There are two common ways to multiply vectors – “Scalar or dot product”: Result is a scalar A B = |A| |B| cos(q) q A B =0 A B =0 – “Vector or cross product”: Result is a vector (not now…) q |A B| = |A| |B| sin(q) A B =0 We can write vector without arrow A B =0 Scalar product • Useful for performing projections. A q A î = Ax î Ay Ax • Calculation is simple in terms of components. A B = (A x )(B x ) + (A y)(B y ) Calculation is easy in terms of magnitudes and relative angles. A B A B cos q Learning Check The product of two vector A and B (see figure) is A =5cm B =5cm A . B = |A| |B| cos(q) =0 |A B| = |A| |B| sin(q)= 25 Part 3 Displacement, Velocity and Acceleration How can we determine a car M is running or not ? A. B. C. D. Use a certain point O (at rest) Measure r = OM If OM unchanged M at rest OM changed car is moving M 0M 0 Displacement • The position of an object is described by its position vector, r • The displacement of the object is defined as the change in its position (final – initial) -ri ∆r = rf - ri ∆r Average Velocity • The average velocity is the ratio of the displacement to the time interval for the displacement • The direction of the average velocity is in the direction of the displacement vector, ∆r The average velocity between points is independent of the path taken Instantaneous Velocity • The instantaneous velocity is the limit of the average velocity as ∆t approaches zero • The direction of the instantaneous velocity is along a line that is tangent to the path of the particle’s direction of motion. • The magnitude of the instantaneous velocity vector is the speed. (The speed is a v Average Acceleration • The average acceleration of a particle as it moves is defined as the change in the instantaneous velocity vector divided by the time interval during which that change occurs. • The average acceleration is a vector quantity directed along ∆v a Instantaneous Acceleration • The instantaneous acceleration is the limit of the average acceleration as ∆v/∆t approaches zero • The instantaneous acceleration is a vector with components parallel (tangential) and/or perpendicular (radial) to the tangent of the path (will see in Chapter 4) Producing an Acceleration • Various changes in a particle’s motion may produce an acceleration – The magnitude of the velocity vector may change – The direction of the velocity vector may change (Even if the magnitude remains constant) – Both may change simultaneously Exercises of today’s lecture Make the figure to show this moving What is displacement of a train from staring point to point at 3 seconds after ? What is the velocity and acceleration of a train?? from staring point to point at 3 seconds after ?