Physics Chapter 1-4 Review PDF

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Its a combination of lecture notes and the text book notes. Great book summary, and review for test....

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What is physics?  The study of the basic nature of matter and the interactions that govern its behavior. Scientific Theory and the Scientific Method  Observation leads to theory explaining it  Theory leads to predictions consistent with previous observations  Predictions of new phenomena are observed. If the observations agree with the prediction, more predictions can be made. If not, a new theory can be made. Scientific Theory and the Scientific Method  Scientific theories: o

Must be testable

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Must be continually tested

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Should be simple

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Should be elegant

 Note: Scientific theories can be proven wrong, but they can never be proven right with 100% certainty Process of Physics  A theory may attempt to explain a wide range of rules of nature or experiments in a simplified fashion. Theories must be testable. Constantly Evolving. Many Rules of Nature. Can be discarded. Greek Theory ~ 2000 years  Usually this takes decades, many scientists, without immediate benefits or implications. Theory of Electricity took 130 years to develop. Even after 100 years, a government official still asked Faraday, “What good will this ever do us?”

Operations with Significant Figures  When multiplying and dividing, the number of significant figures in the final result is the same as the number of significant figures in the least accurate of the factors being combined  When adding or subtracting, round the result to the smallest number of decimal places of any term in the sum Metric Units  Unit of measurement are an essential part in any measurement Conversion of units  When units are not consistent, you may need to convert to appropriate ones  Units can be treated like algebraic quantities that can “ cancel” each other  Example: 15.0 in × 2.54 cm / 1 in = 38.1 cm Problem 1:  A pancake recipe designed to feed 12 people calls for 380 grams of flour. Calculate the quantity of flour required to feed 2 people. (Round the final answer to four decimal place.)  Explanation: This problem is solved using ratios and proportions.  Let N12 and N2 be the number of people.  Let Q12 be the quantity required to feed 12 people.  The above condition can be represented in the form of a proportion and solved as follows:  N2N12×Q12=Q2  212×380 grams=Q2  Q2=63.3333 grams

Problem 2 Length conversion, number of yards in a mile If a mile is 5280 ft long and a yard contains 3 ft, how many yards are there in a mile?  explanation: The number of yards in a mile is calculated as follows:  5280 ft × 1 yard3 ft = 1760 yards  Problem 3 –  Price of gas, conversion of dollars/liter to dollars/gallon  If gas costs $1.60 per liter, how much does a gallon of gas cost? (Round the final answer to four decimal places.)  Explanation: Since 1 gallon = 3.78357 liters, the cost of a gallon is calculated as follows:  $ 1.61 L × 3.78357 L1 gal = $6.0537/gal A unit of volume in the metric system is the  Liter Convert unit. 1. If the height of the bridge is 15 feet, how many meters is this? 2. If the price of meat is 2.99 dollar per pound, how much dollar per kilogram? 3. If the speed limit is 60 mile per hour, how many meters per second is this?

Newtonian Revolution  The study of Physics begins with Newtonian mechanics.  Mechanics is the branch of physics that focuses on the motion of objects and the forces that cause the motion to change.

 There are two parts to mechanics: o Kinematics and Dynamics. o

Kinematics deals with the concepts that are needed to describe motion, without any reference to forces.

o

Dynamics deals with the effect that forces have on motion

Position and displacement  Position is a variable.  Position and distance are similar but not the same. Both use units of length.  Position is given relative to an origin. Speed  Speed is how fast an object changes its location.  Speed is always some distance divided by some time.  Average speed is total distance divided by total time. Instantaneous Speed  Instantaneous speed is the rate at which distance is being covered at a given instant in time.  It is found by computing the average speed for a very short time interval in which the speed doesn’t change appreciably. Velocity  The velocity of an object (v) tells you both its speed and its direction of motion.  Velocity can be positive or negative, so it includes information about the moving object’s direction.  Constant velocity means that both the speed and the direction an object is traveling remains constant.

Average and instantaneous velocity  Average velocity is the total displacement divided by the total time taken.  Instantaneous velocity describes the velocity of an object at one specific moment in time or at one specific point in its path Vectors and Scalars  Physics deals with many physical quantities, which are divided into scalars and vectors.  A scalar quantity is one that can be described by a single number (including any units) giving its size or magnitude.  Examples: Distance, Time, volume, mass, temperature, and density.  A quantity that deals with both magnitude and direction is called a vector quantity. o

Examples: Displacement, Force, weight, and velocity

Uniform Acceleration  Uniform Acceleration is the simplest form of acceleration.  It occurs whenever there is a constant force acting on an object.  Most of the examples we consider will involve constant acceleration.  A falling rock or other falling object.  A car accelerating at a constant rate.  The acceleration does not change as the motion proceeds. How Does a dropped object behave?  Does the object accelerate, or is the speed constant?  Do two objects behave differently if they have: o

Different masses?

o

Different shapes?

Acceleration due to gravity  Earth exerts a gravitational force on objects o

Object is attractive towards Earth’s surface

 Near Earth’s surface, this force produces a constant acceleration downward  Free Fall-all objects moving under the influence of gravity only are said to be in free fall  The acceleration is indicated by g o

g has magnitude and direction

o

g= 9.8 ms^-2

How to measure acceleration due to gravity  Gallilio was the first to accurately measure this acceleration due to gravity  Rolling an object down an inclined plane, he slowed the motion enough to establish that the gravitational acceleration is uniform (Constant)  The acceleration is indicated by g o

G= 9.8 ms-2

Falling ball at equal time interval  Flashes of a stroboscope illuminate a falling ball at equal time intervals.  Distance covered in successive time intervals increases regularly.  Velocity values steadily increase.  Thus, the acceleration is constant.  Calculate the acceleration due to gravity from the graph (g). Example:

 The diagram shows the positions at 0.05- sec intervals of two balls moving left to right. Are either or both of these balls accelerated? o

Both balls are accelerated. Ball A covers an increasing distance in each 0.05-sec interval, so it is speeding up. Ball B is covering less and less distance with each interval, so it is slowing down. Both are accelerations.

Free Falling Object  Free Falling object is defined as the vertical motion of a body at constant acceleration, g under gravitational field without air resistance Tracking a falling object  During each second of free fall, an object’s speed increases  During each second of free fall, an object falls a greater distance because it’s speed is increasing How does a dropped object behave?  Do two objects behave differently if they have: o

different masses?

o

different shapes?

 The feather falls more slowly than the brick.  But what is the REAL reason? o

Air resistance!

 If we drop a feather and a brick in a vacuum, they reach the ground at the same time.  Gravitational acceleration does NOT depend on the weight of the object Beyond Free Fall: Throwing a Ball Upward  What if the ball is thrown upward?

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Gravitational acceleration is always directed downward, toward the center of the Earth.

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Here, the acceleration is in the opposite direction to the original upward velocity.

Throwing a ball upward  Let the initial velocity be 20 m/s upward. o

It immediately starts experiencing a downward acceleration due to gravity, of approximately 9.8 m/s2.

o

Every second, the velocity decreases by 9.8 m/s.

Velocity Graph  The velocity-vs-time plot starts with +20 m/s (upward) at time t=0 and changes at a steady rate of -9.8 m/s2 (decreasing 10 m/s each second).  Positive velocities correspond to upward motion; negative velocities correspond to downward motion.  The slope is constant and negative (for constant downward acceleration). Projectile Motion  The path that a moving object follows is called its trajectory. o

An object thrown horizontally is accelerated downward under the influence of gravity.

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Gravitational acceleration is only vertical, not horizontal.

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The object’s horizontal velocity is unchanged, if we can neglect air resistance.

 Projectile motion involves the trajectories and velocities of objects that have been launched, shot, or thrown. What does the trajectory look like?

 The acceleration of the horizontal motion is zero (in the absence of air resistance). o

The object moves with constant horizontal velocity.

o

It travels equal horizontal distances in equal time intervals.

 The acceleration in the vertical direction is constant. o

Its vertical velocity increases downward just like the falling ball.

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In each successive time interval, it falls a greater distance than in the previous time interval.

Components of Projectile Motion  When projectiles are launched at an angle, the initial velocity has a horizontal and a vertical component. Maximum distance  When you play angry bird, at which angle can you throw the bird the longest distance?  Complementary values of the initial angle result in the same range o

The heights will be different.

 The maximum range occurs at a projection angle of 45o

A Brief History  Where do our ideas and theories about motion come from?  What roles were played by Aristotle, Galileo, and Newton?  Will the chair continue to move when the person stops pushing? o

How did Newton’s theory come about?

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What does it tell us about motion?

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Can we trust our intuition?

Aristotle’s View  A force is needed to keep an object moving.  Air rushing around a thrown object continues to push the object forward.  Galileo’s Contribution  Galileo challenged Aristotle’s ideas that had been widely accepted for many centuries.  He argued that the natural tendency of a moving object is to continue moving. o

No force is needed to keep an object moving.

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This goes against what we seem to experience.

Newton’s Contribution  Newton built on Galileo’s work, expanding it.  He developed a comprehensive theory of motion that replaced Aristotle’s ideas.  Newton’s theory is still widely used to explain ordinary motions.  Sir Isaac Newton was an English mathematician, physicist, astronomer, theologian, and author who is widely recognized as one of the most influential scientists of all time and as a key figure in the scientific revolution. Forces  Contact forces o

Forces which can be exerted by one object on another object on Physical contact (physical touch) is called contact force

 Normal force

o

When an object rests or pushes on a surface, the surface exerts a push on it that is directed perpendicular to the surface.

 Friction Force o

In addition to the normal force, a surface may exert a frictional force on an object, directed parallel to the surface.

 Tension Force o

A pulling force exerted on an object by a rope, cord, etc.

Non contacted force  Forces which can be exerted by one object from distance (even without physical contact with the object) o

Gravitational Force

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Electrical Force

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Magnetic Force

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Nuclear Forces

Net Force  The net force is the vector sum of all the forces acting on a body. o

Fnet = F = F1 +F2 +F3 + 

The net force is the resultant of this vector addition.

 Bold letters represent vectors. The units of Force are Newtons, or the abbreviation N, which represent the SI units: kg-m/s o

SI unit of force is a Newton (N) 1 N=1kg•m/s2

o

US Customary unit of force is a pound (lb) 1 N = 0.225 lb

Free Body Diagrams  The free body diagram (FBD) is a simplified representation of an object, and the forces acting on it. It is called free because the diagram will show the object without its surroundings; i.e. the body is “free” of its environment. Newton’s First Law of Motion: Inertia and Equilibrium  Newton’s 1st Law (The Law of Inertia): o

An object remains at rest, or in uniform motion in a straight line, unless it is compelled to change by an externally imposed force.

 Inertia is a measure of an object’s resistance to changes in its state (motion/station). o

If the object is at rest, it remains at rest (velocity = 0).

o

If the object is in motion, it continues to move in a straight line with the same velocity.

Newton’s Second Law  The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. o

� = ���� / �

 The net force is just the vector sum of all of the forces acting on the body, often written as F. o

If a = 0, then F = 0. This body can have: 

Velocity = 0 which is called static equilibrium, or



Velocity  0, but constant, which is called dynamic equilibrium.

Newton’s Second Law- Net Force  It is the total force or net force that determines an object’s acceleration.

 If there is more than one vector acting on an object, the forces are added together as vectors, taking into account their directions. Newton’s Third Law of Motion  When 2 bodies interact, the forces on the bodies, due to each other, are always equal in magnitude and opposite in direction.  In other words, forces come in pairs. o

Mathematically: F21 = −F12 M

Mass and Weight  What exactly is mass?  Is there a difference between mass and weight?  If something is weightless in space, does it still have mass? Mass vs. Weight  MASS: The amount of matter in an object. measured in kilograms (kg)  WEIGHT: The force of gravity on an object due to the planet it the object is on.  F w = mobjg Newtons. o

An object’s weight is the gravitational force acting on the object.

o

Weight is a force, measured in units of newtons (N).

o

In the absence of gravity, an object has no weight but still has the same mass.

Weight  Weight is the Force of gravity acting on an object in freefall.  Near the surface of the Earth, it is F= mg.  This is mass times the acceleration, g = 9.8 m/sec2

 Always points towards the center of the Earth, or locally downwards Contact Forces  Contact forces: these are forces that arise due to of an interaction between the atoms in the surfaces of the bodies in contact.  Friction  Normal Force  Tension Frictional Forces  Friction: a contact force parallel to the contact surfaces. o

Static friction acts to prevent objects from sliding.

o

Kinetic friction acts to make sliding objects slow down. Sometimes called Dynamic friction.

Tension  This is the force transmitted through a “rope” from one end to the other. o

An ideal cord has zero mass, does not stretch, and the tension is the same throughout the cord....