Introduction to Everyday Physics 1
The Scope of Physics
PRIMARY COURSE GOALS
•To learn some of the basic concepts of physics by studying the behavior of common everyday objects
•Understand how basic concepts of physics provide explanation to everyday experience and answers to questions that relate to our daily activities
•To understand how the behavior of common everyday objects are used in technology and engineering to solve problems in life
•Science refers to a system of acquiring knowledge. This system uses observation and experimentation to describe and explain natural phenomena
Click here Download
•Science is a part of everyday life.•It is evident in the modern technological devices we use everyday
•In this course we will uncover the scientific principles that explain some everyday experiences and the behavior of objects around us
•We will see that what seems like ‘magical’ effects can be understood with just a few basic principles things happen for a reason!
Introduction to Everyday Physics
What Physics is?
•The study of how objects behave (from the very tiny to the very big, and from the beginning of the Universe to its ultimate fate).
•A search for patterns or rules of behavior of the objects in the Universe.
Relation of Physics to the other sciences
•Physics is one of the many branches of Science.
•Obviously, no one branch of science can handle the scope of science
•Each branch of science specializes in studying specific certain aspects of the scope of science. This is referred to as Specialization.
Specialization in Science
•Physics
•Astronomy
•Chemistry
•Biology
•Geology
•Oceanography
•Meteorology
SCIENCE
Physical – inanimate objects
Biological – living things
•All matter, living and non-living, is composed of the same basic ingredients- atoms and molecules
•At the most fundamental level the distinction between living and non-living disappears.
•Clearly, however, human behavior cannot be understood on the basis of either physical or biological science alone
Social Science
is the discipline that investigates
the interrelationships among people
•Sociology
•Psychology
•Political science
•Economics
Physics, the fundamental Science
•Physics is the most fundamental of the natural sciences. Scientists of all disciplines make use of ideas and principles of physics
•Principles of physics play essential role in understanding how human activities affect the atmosphere and the ocean, in the search of alternative sources of energy
•Physics is the foundation of engineering and technology
Scope of Physics
Major subfields of Physics include
•Mechanics: Deals with motion and forces that produces motion
•Thermodynamics: Heat and temperature and their relation to energy and work
•Electricity: Form of energy resulting from the existence of charges
•Magnetism: Phenomenon produced by motion of electric charges that results in attractive or repulsive forces between objects
•Optics: Studies behaviour and properties of light, and the construction of instruments that use or detect light
Scope of Physics
•Condensed-matter physics: Physics of solid and liquids; the largest branch of physics
•Atomic physics: Studies the structure of the atom, its energy states and its interactions with other particles and with electric and magnetic fields
•Nuclear physics: Studies the constituents and interactions of atomic nuclear
•Particle physics: Studies the nature of particles that are the constituents of matter and radiation
•Astrophysics: Space science that applies the laws of physics to explain the birth, life and birth of stars, planets, galaxies etc.
The scientific approach
•Progress in understanding our physical surroundings comes about through observation and measurement
experiment
•Coupled with logic and reason
thought
Measurement and mathematics in physics
•Physics uses quantitative methods to make precise predictions that can be tested by making physical measurements
•Mathematics is a compact language for describing and manipulating results of measurements
•Basic concepts of physics can be described and understood with a minimum of mathematics
Physics and Everyday Phenomena
•Physics provides explanation to everyday experience and answers to questions that relate to our daily activities
•As an example, we study mechanics and illustrate how it answers questions such as
Why do things move?
Why do we wear seatbelts?
Why is it tough to walk on ice?
Why doesn’t the moon fall into the earth?
How do airbags protect you in a crash?
Etc
Describing Motion
•Displacement and distance
Displacement of an object is change in the position of the object. An arrow drawn from the initial position to the final position represents its displacement
•Displacement is not
the same as distance
•Displacement is a
vector while distance
is a scalar
•A vector has both
magnitude and direction
while a scalar has only
magnitude
displacement
Concepts: speed and velocity
• Speed: How fast am I going?
measured in kilometers per hour (km/h),
meters per second (m/s) miles per hour
(mph), feet per second (ft/s) etc
distance
speed distance ÷ time
time
Click here Download
Velocity includes speed and direction•Velocity of an object is its displacement divided by the time interval in which the displacement occurred
•Velocity conveys information both about the speed (magnitude) and direction, not only how fast, but also in what direction
•Average velocity is
•For a straight-line motion, the average velocity is
Example
•How many days would it take to walk a distance of 2665 miles if you walked continuously at 5 mph?
•d = v t t = d/v = 2665 miles/5 miles/hr = 533 hours
•In days: 533 hours/24 hr/day ~ 22 days
Time (seconds)
Example
Which graph represents the motion with the highest average velocity?
Acceleration
•Rate of change of velocity with time is acceleration.
where is change in velocity and is time interval in which velocity change occurred
•Like velocity, acceleration is a vector
•By definition, if an object has a constant velocity, its acceleration is zero
•Velocity, like any other vector, is constant when its magnitude and direction are constant.
Average acceleration is
Acceleration
•Any change in velocity is acceleration
•If you speed up (velocity increases), there is acceleration
•If you slow down (velocity decreases) there is acceleration – we call this deceleration – putting on the brakes!
•If you turn (change direction) there
is acceleration
You are accelerating if
•You are going down a steep hill on rollerblades (your velocity increases)
•In an elevator when it starts to go up (you are at rest then start moving)
•In a car going around a curve at constant speed (the direction of your velocity changes)
•You are on a bus that is slowing down (your velocity decreases)
•You are in an elevator and the cable breaks (you will accelerate downward)
Why does something move?Because nothing stops it!
Newton’s First and Second Laws of motion
The laws of motion – Why things move
•Galileo’s principle of inertia (Newton’s 1st law)
•Newton’s 2nd law - law of dynamics F(force) = m a (mass x acceleration)
•Newton’s 3rd law - “for every action there is an equal and opposite reaction”
Galileo’s principle of Inertia
•A body at rest tends to remain at rest
•A body in motion tends to remain in motion
Or stated in another way:
•You do not have to keep pushing on an object to keep it moving
•If you give an object a push, and if nothing tries to stop it, (like friction) it will keep going
What is inertia?
•All objects have it
•It is the tendency to resist changes in velocity
–if an object is at rest, it stays at rest
–if an object is moving, it keeps moving
•Mass is a measure of the inertia of a body, in units of kilograms (kg)= 1000 grams
•Mass is NOT the same as weight !
Newton’s First Law of Motion Refined Law of Inertia
•No force (push or pull) is needed to make an object move with constant velocity
•Constant velocity- moving in a straight line with constant speed
No stopping, no speeding and no turning
Note that a body at rest has a constant velocity of zero
Inertia examples
•Pull the tablecloth out from under the dishes
•Knock the card out from under the marble
•Shake the water off of your hands
•The car on the air track keeps going
•What happens when you do not wear your seatbelt and your car suddenly crashes into a big tree?
•Tightening a hammer-head by repeatedly hitting the bottom of the handle on the table while holding the hammer upright
•A passenger in a car will smash through the windscreen if the car comes to a sudden stop (unless, of course, he is held in his seat by a seat belt)
•Passengers fall forward when a vehicle decelerates to a stop and fall backward when it accelerates from rest
•The process of freeing, say a coat, from dust by shaking it
•Throwing a ball up and down while walking
•Dribbling a basketball while running
Dogs use the principle of inertia!
Bart is on a train that is moving with a constant velocity. He then jumps straight up on the moving train
Will he land:
1) on the ground, or
2) on the train?
Bart maintains his forward motion even as he jumps up. He lands on the train.
Physics and Ice Hockey
No force is needed to keep the puck moving
forward after it leaves the player’s stick.