Physics 201 –College Physics. Lectures MWF 1:50-2:40 E-mail firstname.lastname@example.org Phone: 458-7967 office / 845-6015 lab Office Hours: ? or by appointment, Office: MPHYS 303 Web-site: http://people.physics.tamu.edu/a-sattarov/. Akhdiyor Sattarov.
Lectures MWF 1:50-2:40
Phone: 458-7967 office / 845-6015 lab
Office Hours: ? or by appointment,
Office: MPHYS 303
Text: Physics 8th ed by Young & Geller with Mastering Physics; PHYS 202 Lab Manual
Example: A small rock thrown upward – we can neglect the air resistance
Earth orbiting around Sun, we can treat Earth as point particle because the radius of Earth much smaller than the dimensions of the system
Length meter=distance traveled in vacuum by light during 1/299792458 of sec
Time second-9,192,631700 times the period of oscillations of radiation from the cesium atom.
Mass kilogram=90% Platinum 10% iridium alloy cylinder h=d=0.03917m
Since we will work with very small and very big systems we have to have conversion multipliers
Power of 10 Prefix Abbreviation
10-6 micro- m
10-3 milli- m
10-2 centi- c
103 kilo- k
106 mega- M
109 giga- G
In Physics, the word dimension denotes the physical nature of a quantity
distance between 2 points can be measured in meters, centimeters, feet etc. – different ways of expressing the dimension of length
Example: Volume of a cube of water, L=2m
Example: Find mass of water, density of water 997 kg/m3
Example: Express speed of light 3x108 m/s in km/h
You can not add or subtract quantities that have different units
It will help you to check dimensional consistency of your result!!
3kg+15m means something is wrong
Mass=r2*V=(997kg/m3)2 8m3= ****** kg2/m3 - something is wrong
We have to develop basic and reliable method of keeping track of those uncertainties in subsequent calculations.
Example: Let we have to measure area of a rectangular plate with a meter stick. Suppose that we can measure particular side with 0.1cm accuracy. Suppose that side a=16.3cm and side b=4.5cm.
so our area 73+/-2cm – note that the answer has two significant figures
In our example First term had 3 and the second 2 significant figures
In multiplying (dividing) two or more quantities, the number of significant figures in the final result is no greater than the number of significant figures in the term that had fewest significant figures.
In addition (subtraction) two or more quantities the final result can have no more decimal places than the term with fewest decimal places
Magnitude of a vector
We say that A=D
We say A=-E
Let have several vectors
We say that vectors are parallel
We say that vectors are antiparallel
Resulting Vector is collinear (parallel or anti parallel) to the original vector.
BAdding vectors: Tail to tip method
2 vectors are along two sides of a parallelogram
Resulting vector along the diagonal of the parallelogram that starts at the tails of the vectors
Sum of 3 vectors
It is in the direction of the vector A, but has a unit length and it is dimensionless.
Ay – y-component of vector A
Ax – x-component of vector AComponents of vectors (2d)
Let define angle between vector and positive x-direction
Components are not vectors
They can be positive and negative, depending on an angle
A vector can be represented in 2 ways
a) by its components
b) By its magnitude and angle with positive x-direction (in 3d case also angle with positive z-direction)
A person starts from point A and arrives at point B. Find components, magnitude of the position vectors and angle between the vector and x-axis. Find the displacement vector.
Pay attention!! You may get this angle
Example 1.45: Vector A has components Ax=1.3cm, Ay=2.25cm; vector B has components Bx=4.1cm and By=-3.75cm. Find
the components of the vector sum A+B;
The magnitude and direction of A+B;
The components of the vector difference B-A;
The magnitude and direction of B-A;
Example1.50 A postal employee drives a delivery truck along the route shown in figure below. Use components to determine the magnitude and direction of the truck’s resultant displacement. Then check the reasonableness of your answer by sketching a graphical sum.
Kinematics – describes the motion of object without causes that leaded to the motion
We are not interested in details of the object (it can be car, person, box etc..). We treat it as dimensionless point
We want to describe position of the object with respect to time – we want to know position at any given time
Path (trajectory) – imaginary line along which the object moves
Very often I will write rn instead of r(tn), the same for the components of the vector, for example, yn instead of y(tn)
t=t3Motion along a straight line