Physics → the science of matter and energy and their interaction with each other. The Role of Physics in Science
In a broader sense, physics can be seen as the most fundamental of the natural sciences. Chemistry, for example, can be viewed as a complex application of physics, as it focuses on the interaction of energy and matter in chemical systems. We also know that biology is, at its heart, an application of chemical properties in living things, which means that it is also, ultimately, ruled by the physical laws.
Branches of Physics
1. Mechanics is the branch of Physics dealing with the study of motion 2. Heat and Thermodynamics-the physics of heat
3. Electromagnetism-the study of electrical and magnetic fields, which are two aspects of the same phenomenon 4. Waves, Acoustics, and Optics
5. Modern Physics
-a logical and scientific way of finding a solution to a certain problem -The goals of the scientific method are uniform, but the method itself is not necessarily formalized among all branches of science. It is most generally expressed as a series of discrete steps, although the exact number and nature of the steps varies depending upon the source. Steps:
1. Identification of the problem-determine a natural phenomenon (or group of phenomena) that you are curious about and would like to explain or learn more about, then ask a specific question to focus your inquiry. 2. Gathering Data and Observation-this step involves learning as much about the phenomenon as you can, including by studying the previous studies of others in the area. 3. Formulate a hypothesis – using the knowledge you have gained, formulate a hypothesis about a cause or effect of the phenomenon, or the relationship of the phenomenon to some other phenomenon. * Null Hypothesis- it suggest the absence of a relationship between independent and dependent variable * Alternative Hypothesis- suggest the presence of relationship 4. Test the hypothesis – plan and carry out a procedure for testing the hypothesis (an experiment) by gathering data.
5. Analyze the data – use proper mathematical analysis to see if the results of the experiment support or refute the hypothesis. TRIVIA!
A rubber band shrinks when heated and expands when cooled because of the change in its Entropy state.
If you yelled for 8 years, 7 months and 6 days, you would have produced just enough sound energy to heat up one cup of coffee.
What are Vectors and Scalars?
Vectors- requires both magnitude and direction for its complete description -a physical quantity
Scalar- requires magnitude for its complete description
-a physical quantity expressed in terms of magnitude alone
Direction And Magnitude
All of the previous development has been limited to the case of motion along a straight line. We’ll treat motion in two dimensions and eventually in three dimensions. These extensions require that we make use of the vector property of displacement and velocity. If we wish to describe the motion of an automobile, we could say that the speed is 60 mi/hr. However this is not a complete specification of the motion; more information is contained in the statement that the velocity is 60 mi/hr in the direction northeast. Velocity is a quantity that has both magnitude and direction. Such quantities are called vectors. Another such quantity is displacement: an object may move a certain distance but the vector description must include the direction of motion as well as the distance travelled. Quantities that are completely specified by magnitude alone are called scalars. Mass, time, and temperature, for example, are scalar quantities. As we use the terms in physics, speed and velocity are not identical: speed is a scalar, velocity is a vector. We shall use the term “speed” when we are interested only in the rate at which an object moves and are not concerned with the direction of the motion. When we wish to convey the impression that direction as well as magnitude is important, the term “velocity” will be used.
Acceleration is a Vector
In addition to displacement and velocity, we also require for the complete description of motion, the vector property of acceleration. The magnitude of the acceleration of an object is the rate of change of the velocity, and the direction of the acceleration is the direction of the change in velocity.
Lightning strikes about 6,000 times per minute on our planet.
Coin, playing card, small cup
1. Place the playing card on the small cup.
2. Place the coin on the playing card.
3. Push the card quickly by flicking your finger. Observe.
1. What happens to the coin as you flick it with your finger? 2. Why do you think the coin does not move with the card?
What is Kinematics?
Kinematics, branch of physics and a subdivision of classical mechanics concerned with the geometrically possible motion of a body or system of bodies without consideration of the forces involved (causes and effects of the motions).
Kinematics aims to provide a description of the spatial position of bodies or systems of material particles, the rate at which the particles are moving (velocity), and the rate at which their velocity is changing (acceleration). When the causative forces are disregarded, motion descriptions are possible only for particles having constrained motion—i.e., moving on determinate paths. In unconstrained, or free, motion, the forces determine the shape of the path.
For a particle moving on a straight path, a list of positions and corresponding times would constitute a suitable scheme for describing the motion of the particle. A continuous description would require a mathematical formula expressing position in terms of time.
When a particle moves on a curved path, a description of its position becomes more complicated and requires two or three dimensions. In such cases continuous descriptions in the form of a single graph or mathematical formula are not feasible. The position of a particle moving on a circle, for example, can be described by a rotating radius of the circle, like the spoke of a wheel with one end fixed at the centre of the circle and the other end attached to the particle. The rotating radius is known as a position vector for the particle, and, if the angle between it and a fixed radius is known as a function of time, the magnitude of the velocity and acceleration of the particle can be calculated. Velocity and acceleration, however, have direction as well as magnitude; velocity is always tangent to the path, while acceleration has two components, one tangent to the path and the other perpendicular to the tangent.
V. Laws of Motion
What are the Three Laws of Motion?
Newton’s laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. They have been expressed in several different ways over nearly three centuries.
An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This law is often called
“The law of Inertia”.
What does this mean?
This means that there is a natural tendency of objects to keep on doing what they’re doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
What does this mean?
Everyone unconsciously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects. However, the Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation: F=MA
FORCE = MASS times ACCELERATION
Mike’s car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton’s Second Law, you can compute how much force Mike is applying to the car. F=MA
=1,000kg x 0.05m/s/s
= 50 Newtons
For every action there is an equal and opposite re-action.
What does this mean?
This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the oppositedirection equally hard.
1. Who proposed the law of motion that for every action there is an equal and opposite reaction? A. Albert Einstein B. Isaac Newton C. Galileo
2. Which branch of science deals with the study of motion, forces, & energy? A. Physics B. Chemistry C. Astronomy
VI. Impulse and Momentum
The momentum of a body is equal to its mass multiplied by its velocity. Momentum is measured in N s. Note that momentum is a vector quantity, in other words the direction is important. Impulse
The impulse of a force (also measured in N s) is equal to the change in momentum of a body which a force causes. This is also equal to the magnitude of the force multiplied by the length of time the force is applied.
Impulse = change in momentum = force × time
Conservation of Momentum
When there is a collision between two objects, Newton’s Third Law states that the force on one of the bodies is equal and opposite to the force on the other body. Therefore, if no other forces act on the bodies (in the direction of collision), then the total momentum of the two bodies will be unchanged. Hence the total momentum before collision in a particular direction = total momentum after in a particular direction. TRIVIA!
Radar is an abbreviation of Radio Detection And Ranging.
VII. Work, Power, & Energy
Work can be defined as transfer of energy. In physics we say that work is done on an object when you transfer energy to that object. If one object transfers (gives) energy to a second object, then the first object does work on the second object. Work is the application of a force over a distance. Lifting a weight from the ground and putting it on a shelf is a good example of work. The force is equal to the weight of the object, and the distance is equal to the height of the shelf (W= Fxd). Work-Energy Principle –The change in the kinetic energy of an object is equal to the net work done on the object. Energy can be defined as the capacity for doing work. The simplest case of mechanical work is when an object is standing still and we force it to move. The energy of a moving object is called kinetic energy. For an object of mass m, moving with velocity of magnitude v, this energy can be calculated from the formula E= 1/2 mv^2. Types of Energy
There are two types of energy in many forms:
Kinetic Energy = Energy of Motion
Potential Energy = Stored Energy
Forms of Energy
Solar Radiation — Infrared Heat, Radio Waves, Gamma Rays, Microwaves, Ultraviolet Light Atomic/Nuclear Energy -energy released in nuclear reactions. When a neutron splits an atom’s nucleus into smaller pieces it is called fission. When two nuclei are joined together under millions of degrees of heat it is called fusion Electrical Energy –The generation or use of electric power over a period of time expressed in kilowatt-hours (kWh), megawatt-hours (NM) or gigawatt-hours (GWh). Chemical Energy –Chemical energy is a form of potential energy related to the breaking and forming of chemical bonds. It is stored in food, fuels and batteries, and is released as other forms of energy during chemical reactions. Mechanical Energy — Energy of the moving parts of a machine. Also refers to movements in humans Heat Energy — a form of energy that is transferred by a difference in temperature What is Power
Power is the work done in a unit of time. In other words, power is a measure of how quickly work can be done. The unit of power is the Watt = 1 Joule/ 1 second. One common unit of energy is the kilowatt-hour (kWh). If we are using one kW of power, a kWh of energy will last one hour. Calculating Work, Energy and Power
WORK = W=Fd
Because energy is the capacity to do work , we measure energy and work in the same units (N*m or joules). POWER (P) is the rate of energy generation (or absorption) over time:P = E/t Power’s SI unit of measurement is the Watt, representing the generation or absorption of energy at the rate of 1 Joule/sec. Power’s unit of measurement in the English system is the horsepower, which is equivalent to 735.7 Watts. TRIVIA!
Due to the effect of Thermal Expansion, the Eiffel Tower is up to 15cm taller in summer.
The only rock that floats in water is pumice.
VIII. Free Fall
A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only by the force of gravity is said to be in a state of free fall. There are two important motion characteristics that are true of free-falling objects:
Free-falling objects do not encounter air resistance.
All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s (often approximated as 10 m/s/s for back-of-the-envelope calculations) Because free-falling objects are accelerating downwards at a rate of 9.8 m/s/s, a ticker tape trace or dot diagram of its motion would depict an acceleration. The dot diagram at the right depicts the acceleration of a free-falling object. The position of the object at regular time intervals – say, every 0.1 second – is shown. The fact that the distance that the object travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward. Recall from an earlier lesson, that if an object travels downward and speeds up, then its acceleration is downward.
Free-fall acceleration is often witnessed in a physics classroom by means of an ever-popular strobe light demonstration. The room is darkened and a jug full of water is connected by a tube to a medicine dropper. The dropper drips water and the strobe illuminates the falling droplets at a regular rate – say once every 0.2 seconds. Instead of seeing a stream of water free-falling from the medicine dropper, several consecutive drops with increasing separation distance are seen. The pattern of drops resembles the dot diagram shown in the graphic at the right. IX. Projectile Motion
What is Projectile Motion?
Projectile motion is a form of motion where a particle (called a projectile) is thrown obliquely near the earth’s surface, it moves along a curved path under the action of gravity. The path followed by a projectile is called its trajectory. A few examples of this include a soccer ball being kicked, a baseball being thrown, or an athlete long jumping. Even fireworks and water fountains are examples of projectile motion.
Buoyant forces act on the foundations of buildings. Tokyo underground train stations need to be pinned down to avoid bobbing to the surface from the buoyant forces caused by increasing water levels. B = Fbottom − Ftop|
B = PbottomA − PtopA = (ρfluidghbottom − ρfluidghtop)A| B = ρfluidgΔhA = ρfluidgV = mfluidg|
B = Wfluid|
* Archimedes’ principle: The buoyant force (B) on an object immersed in a fluid is equal to the weight of the fluid displaced.
* Pascal’s Principle
Pascal’s principle, also called Pascal’s law, in fluid (gas or liquid) mechanics, statement that, in a fluid at rest in a closed container, a pressure change in one part is transmitted without loss to every portion of the fluid and to the walls of the container. The principle was first enunciated by the French scientist Blaise Pascal. Pressure is equal to the force divided by the area on which it acts. According to Pascal’s principle, in a hydraulic system a pressure exerted on a piston produces an equal increase in pressure on another piston in the system. If the second piston has an area 10 times that of the first, the force on the second piston is 10 times greater, though the pressure is the same as that on the first piston. This effect is exemplified by the hydraulic press, based on Pascal’s principle, which is used in such applications as hydraulic brakes. Pascal also discovered that the pressure at a point in a fluid at rest is the same in all directions; the pressure would be the same on all planes passing through a specific point. This fact is also known as Pascal’s principle, or Pascal’s law.
* Bernoulli’s Principle
Bernoulli’s principle, sometimes known as Bernoulli’s equation, holds that for fluids in an ideal state, pressure and density are inversely related: in other words, a slow-moving fluid exerts more pressure than a fast-moving fluid. Since “fluid” in this context applies equally to liquids and gases, the principle has as many applications with regard to airflow as to the flow of liquids. One of the most dramatic everyday examples of Bernoulli’s principle can be found in the airplane, which stays aloft due to pressure differences on the surface of its wing; but the truth of the principle is also illustrated in something as mundane as a shower curtain that billows inward. XI. Pressure
Pressure is the ratio of force applied per area covered … P = | F|
The unit of pressure is the pascal
Pa=N=kg m/s2 = kg
m2 m2 m s2
The pascal is also a unit of stress and the topics of pressure and stress are connected.
Many physicists believe wormholes (a “shortcut” through space and time) exist all around us but they are smaller than atoms. Hawaii is moving toward Japan 10cm (4in) every year.
When hydrogen burns in the air, water is formed.
Diamonds are the hardest known substance.
Sunlight can penetrate clean ocean water to a depth of 73m (240ft).
Laser is an abbreviation of Light Amplification by Stimulated Emission of Radiation.