Nota Fizik: Analysing scientific investigation

A variable is a quantity that can vary in value.

Manipulated variable is a variable that is set or fixed before and experiment is carried out. it is usually plotted on x- axis.

Responding variable is a variable that changes according to and dependent to manipulated variable. it is usually plotted on y-axis.

Fixed variable is fixed and unchanged throughout the experiment.

Inference: state the relationship between two VISIBLE QUANTITIES in a diagram or picture.

Hypothesis: state the relation ship between two MEASURABLE VARIABLES that can be investigated in a lab.

How to tabulate data?

-the name or the symbols of the variables must be labelled with respective units.
-all measurements must be consistent with the sensitivity of the instruments used.
-all the calculated values must be correct.
-all the values must be consistent to the same number of decimal places.

A graph is cosidered well-plotted if it contains the following:
- a title to shoe the two variables and investigation.
- two axes labelled with correct variables and units
- scales must be chosen carefully and graph must occupy more than 50% of the graph paper.
-all the points are correctly drawn.
-the best line is drawn.

Electromagnetic Spectrum

Electromagnetic Spectrum

When you watch television, listen to the radio or cook something in a microwave oven , you are actually using electromagnetic waves.

Electromagnetic waves are propagating waves in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation.

Electromagnetic waves carries energy and momentum which may be imparted when they interact with matter.

Electromagnetic waves comprise of a series of waves whose frequencies and wavelengths extend over a broad range.

Waves in the electromagnetic spectrum vary in size from very long radio waves to very short gamma rays.

Visible light waves are the only electromagnetic waves we can see. We see these waves as the colours of the rainbow. Each colour has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light.

When white light shines through a prism or through water vapour, the white light is broken apart into the colours of the visible light spectrum.

The electromagnetic spectrum is the range of frequencies and wavelengths over which electromagnetic waves are propagated.

Sources of Electromagnetic Waves.

Matter is made up of elementary particles called atoms.

Every atom has a nucleus at its centre which is surrounded by orbiting electrons.

Electrons are charged particles and they move around the nucleus in orbits, each of which is a t a specific energy level. When a charged electron moves from an orbit with a particular energy level to one of a lower energy level, electromagnetic waves are emitted.

Electromagnetic waves are also produced when a charged particle (electron or nucleus) oscillates.

Properties of electromagnetic waves

Electromagnetic waves are:

a. Transverse waves
b. Do not require a medium to propagate and can travel in a vacuum.
c. The magnetic and electric field components of the wave oscillate at right angles to each other and to the direction of propagation of the wave.
d. Obey the wave equation c = fλ. c is the velocity of light, f is the frequency of the wave and the λ is the wavelength.
e. In a vacuum , the waves travel at the speed of light c = 3 X 10^8 ms-1.
f. Undergo the same phenomena as light: reflection, refraction, diffraction and interference.
g. The waves are electrically neutral.
h. Show characteristics of polarization.
i. Energy is transferred by the waves.

In a vacuum, c is a constant for all elecgromagnetic waves The formula c = fλ shows that the frequency f is inversely proportional to the wavelength λ.

The velocities of an electromagnetic wave in other media are different from its velocity in vacuum.

Applications of Pascal's Principle in Everyday Life

A hydraulic system is a device in which a small applied force can give rise to a larger force.

The principle in the hydraulic system is widely used in jacks, vehicle brake systems, hydraulic presses and heavy machinery.

Hyraulic Jacks
Hydraulic jacks are used to lift a heavy load such as when changing a car tyre. When the handle is pressed down, a valve closes and the small piston forces hydraulic fluid through another valve to the larger cylinder. The pressure transmitted results in a large force on the load.


When the handle is raised, valve B closes and hydraulic fluid flows from the buffer tank through valve A into the small cylinder. The handle is moved up and down repeatedly until the load is sufficiently lifted up.

The large piston can be lowered at the end by opening the release valve to allow all the hydraulic fluid to flow back into the buffer tank.

Hydraulic Brakes

Hydraulic brakes are used in cars, lorries and motorcycles.

In a hydraulic brake system, a liquid, known as brake fluid,
is used to transmit pressure from the brake pedal to all the wheels of the vehicle.

When the brake pedal is pressed, the piston of the control cylinder applies a pressure on the brake fluid and this pressure is transmitted, via a system of pipes, to each cylinder at the wheels.

The cylinder at the wheels cause a pair of pistons to push a pair of friction pads to press against the surface of the brake discs or brake drums. The frictional forces between these brake components cause the vehicle to slow down and stop.

When the brake pedal is released, a spring restores the brake discs to their original positions.


Hydraulic Pumps

Hydraulic pumps are used to raise cars in a motor workshop.

The machine is equipped with a small cylinder connected to a large cylinder. Both cylinders are filled with oil.

Compressed air is introduced into the small cylinder in which the compressed air exerts a pressure on the surface of the oil.

This pressure is transmitted by the oil to the large cylinder where the pressure acts on a large piston to produce a force which is large enough to lift a car.

Nota Fizik: Analysing scientific investigation

A variable is a quantity that can vary in value.

Manipulated variable is a variable that is set or fixed before and experiment is carried out. it is usually plotted on x- axis.

Responding variable is a variable that changes according to and dependent to manipulated variable. it is usually plotted on y-axis.

Fixed variable is fixed and unchanged throughout the experiment.

Inference: state the relationship between two VISIBLE QUANTITIES in a diagram or picture.

Hypothesis: state the relation ship between two MEASURABLE VARIABLES that can be investigated in a lab.

How to tabulate data?

-the name or the symbols of the variables must be labelled with respective units.
-all measurements must be consistent with the sensitivity of the instruments used.
-all the calculated values must be correct.
-all the values must be consistent to the same number of decimal places.

A graph is cosidered well-plotted if it contains the following:
- a title to shoe the two variables and investigation.
- two axes labelled with correct variables and units
- scales must be chosen carefully and graph must occupy more than 50% of the graph paper.
-all the points are correctly drawn.
-the best line is drawn.

Applications of Bernoulli's Principle

 The flight of an aeroplane is based on the principle about the effect of the flow of air around its wings, which is, the aerofoil.
- An aerofoil shape has a rounded front edge and pointed (sharp) trailing edge. The top surface is arched (curved) and the bottom is flat.
-When a wing in the form of aerofoil moves through air, the flow of the air over the top has to travel faster to cover the longer distance (compares the lower portion) and creates a region of low pressure. The flow of air below the wing is slower resulting in a region of higher pressure.
-The difference between the pressures at the top and the bottm creates a NET UPWARD FORCE..(remember! bottom part higher pressure..upper part lower pressure).This is called a Lift and helps the plane to take off.
-In addition to that, inverted aerofoils are used in racing cars to create a donward force and stabilize the cars at high speed.

2. Bunsen Burner

- When a bunsen burner is connected to a gas supply, the gas flows at high velocity through a narrow passage in the burner, creating a region of low pressure.
- The outside air, which is at atmospheric pressure, is drawn in an mixes with the gas.
-The mixture of gas and air enables the gas to burn completely to produce a clean, hot fire.

Other applications that you must read on your own.

- Hydrofoil Boat
- Insecticide Spray (or whatever sprays that available)
- The shape of canvas roof ( in car) when its moving - why the roof bulges upward?
- Carburettor
- Curve Ball Spin offs
- The shape of a ski-jumper's body when he's jumping..its curved right? Why?

All the best

What is Physics?

What is Physics?

Physics is a branch of science which studies physical and natural phenomena around us.

Examples of natural phenomena are formation of rainbow, solar eclipse, the fall of things from up to down, the cause of sunset and sunrise, formation of shadow and many more.

Physics mostly answers whys rather than what and it gives scientific, systematic and consistent explanation based on the concepts of physics.

Physics knowledge will increase as the flow of time; new concepts will replace old concepts if proven to be accurate.

The word physics evolved from ‘physikos’ a Greek word for nature.

There are two main divisions of physics which are:
a. Classical physics: motion and energy, mechanics, force and motion, heat, sound, electricity, magnetism and light.
b. Modern physics: atomic, molecular and electron physics, nuclear physics, relativity, origin of universe, astrophysics.

Topics learnt in form 4 are:

1. Introduction to physics
2. Forces and motion
3. Forces and pressure
4. Heat
5. Light



Topics in form 5 would be:

1. Waves
2. Electricity
3. Electromagnetism
4. Electronics
5. Radioactivity

Several discoveries and contributions based on the knowledge of physics:

1911 –New Zealand-born British physicist Ernest Rutherford (UK, New Zealand), proposed that an atom has a positively charged nucleus called Proton.
1957 –Sputnik I, first satellite to orbit the earth (Soviet Union).
1969 –Man landed on the moon – Neil Armstrong became the first human being to set foot on the moon (US).
1989 –www was launched by British Engineer Tim Berners-Lee and his colleague (UK).
1990 –The Hubble Space Telescope was built and launched into orbit by NASA (US).

Among the important figures in Physics:
Galileo Galilei
Isaac Newton
Charles Augustin de Coulomb
Albert Einstein
Stephen William Hawking

Study of Physics

1. As the other branches of science, scientific skills is necessary in the process of undertaking research and analysis in physics.

2. Research or Experiments are done systematically and step by step based on scientific method.

3. Scientific method

Identifying Problem ---- Making Hypothesis -----Planning investigation ------Identifying and controlling variables ----conducting experiment ----collecting data ----recording data----making conclusions---writing reports.


Careers in Physics included (examples)
1. Engineering
2. Computer Science
3. Industry
4. Communication
5. Electronics
6. Medicine – X ray
7. Environmental Science
8. Basic Research

Uses of Gas Laws

1.Bicycle Pump

When the piston is pushed into the cylinder, the air in the cylinder is compressed.

According to Boyle's Law, the air pressure inside the cylinder will increase.

This causes the air pressure in the cylinder to become higher than the pressure inside the tyre. Therefore, the air can flow into the tyre.

2. Hot-air baloon

When the air in a balloon is heated at atmospheric pressure, its temperature will increase.

According to Charles' Law, the volume of gas in the balloon will increase when its temperature increases.

Thus, the upward thrust on the balloon will increase when the volume of air displaced by the balloon increases.

Therefore, the balloon will climb upwards if the upward thrust exceeds the weight of the balloon.

3. Car Tyre

When a car is moving, the car tyre will experience frictional force and compression. This condition causes the temperature of the air inside the tyre to increase.

According to the Pressure Law, the rise in tyre temperature will cause the pressure inside the tyre to increase until an optimum level. Therefore, it is wise to pump the tyre just slightly below the recommended level. Anyway, we must also adjust the pressure of the tyre according to the temperature when we pump the tyre.

Radioactive Detectors

Radioactive Detectors

Geiger-Muller Tube

1. The Geiger-Muller tube is an effective radioactive detector. It can trace alpha particles, beta particles and gamma rays.
2. The outer part of the G-M tube is made of aluminium which acts as the cathode.
3. The middle part of the G-M tube is a metal wire which acts as the anode.
4. The G-M tube is filled with argon gas at low pressure.
5. Initially, the G-M tube must be connected to a high voltage before being used.
6. This high voltage causes some ionization of argon gas.

Cloud Chamber

1. The cloud chamber is made by using a transparent plastic box. The space in it is divided into two parts by a metal.
2. The lower part is filled with solid carbon dioxide. Sponge is used to push the solid carbon dioxide towards the metal plate.
3. The upper part is filled with molecules of alcohol vapour released from the felt which is initially soaked in alcohol.
4. When the alcohol vapour diffuses downwards, it will become colder. Thus, a supersaturated condition will be produced in the space in the lower part of the chamber.
5. When the radioactive rays enter the upper part, the ionization of air will occur. Saturated alcohol vapour will move above the ions. Droplets of liquid alcohol on the ions will cause the formation of misty tracks.
6. Steps to ensure clear tracks:
• The transparent Perspex cover is rubbed with a soft cloth to produce charges which will remove all ions in the chamber before any radioactive rays enter.
• The cloud chamber must be placed horizontally to ensure smooth flow of particles in it.
• If light is used, it must shine on the area superated with vapour and not on the black base of the chamber in order to avoid heating it.
7. Normally, the tracks produced are not uniform. This shows that the radioactive rays are produced randomly.
8. There are three types of tracks as shown in Table below.

Types of radioactive rays	Explanation
Tracks of alpha particles	The alpha tracks are thick and straight. This shows that alpha particles have the strongest ionizing power and the biggest mass.
Tracks of beta particles	The beta tracks are thin and curvy. This shows that beta particles have low ionizing power and small mass.
Tracks of gamma ray	Their tracks are short, curvy and spiky from the middle. It shows that it has the lowest ionizing power.

9. The number of radioactive tracks produced will decrease after a while. This is because after some time, the condensation of alcohol vapour on the radioactive source will block the emission of radioactive rays.

Spark counter

1. The wire gauze and thin wire are connected to a voltage of more than 2000 V.

2. The voltage is increased slowly until sparks are produced in between.

3. The sparks are formed due to ionisation of the air.

4. The voltage is then decreased until no sparks are formed.

5. The radioactive source is brought close to the wire gauze.

6. The radioactive rays will ionize the air molecules between the wire gauze and thin wire. Positively charged ions will be attracted to the negatively charged gauze and the negatively charged ions will be attracted to the positively charged thin ions.

7. Secondary ionization will occur due to the collision between the ions and the air molecules.

8. Therefore, sparks are formed.

9. The number of sparks measured the intensity of radioactive rays from its source randomly.

10. The spark counter can only trace alpha particles which have high ionizing power.

Electroscope

1. When charged plate of the electroscope is exposed to the source of alpha particles, the gold leaf will collapse slowly.

2. This is due to the ions and electron are produced by the alpha particles which will neutralize the charge in the electroscope.

3. The rate of collapse of the gold leaf indicates the strength of the radioactive source.

Photographic Plate

1. All types of radioactive rays will darken the photo film. The effect is like sunlight acting on it.

2. The ionization effect by the radioactive rays will decompose silver bromide crystals on the film.

3. Films which are exposed to sunlight will show white lines representing radioactive tracks.

4. Films are kept in the badges worn by workers as a tracer device of radioactive rays.

5. The main disadvantage of using a film as a radioactive tracer is that it needs to be processed in order to prove the presence of radioactive rays

Half Life

Half-life

Concept of Half-life

1. The reactivity or activity of a radioactive material is the rate of decay of the material.

2. The rate of decay is the same as the number of atoms which decay or are emmited every second.

3. The rate of decay of a radioactive materials depends on the number of atoms that have not yet undergone decay. Thus, the reactivity of a radioactive material will decrease with time.

4. The half-life of a radioactive element is the time taken for half the number of atoms in a sample of radioactive atoms to decay.

Decay curve.

1. The half-life of the same radioactive element is the same but the half-lives of different radioactive elements are different.

2. The value of half-life is not influenced by factors such as temperatures, pressure and etc.

Usage of Half-life

Half-life in Archeology

1. Carbon-14 has a half-life of 5600 years.

2. Humus, animals and plants absorb carbon-14 through carbon dioxide gas in the atmosphere. A small amount in CO2 exists as carbon-14.

3. Living animals and vegetable have a constant amount of Carbon-14 because the c-14 decayed will always replaced.

4. However or dead beings the amount of C-14 in it will decrease because new C-14 will not be absorbed causing its reactivity to decrease.

5. When an antique or human skill are found, their age can be determined by

· Measuring the reactivity of C-14 in it.

· Determine the ratio of decay carbon-14 against intact carbon-14.

Uses of Radioisotopes

Uses of Radioisotopes

Radioisotopes

1. Radioisotopes are isotopes with radioactive properties.

2. Isotopes are elements whose atoms have the same number of proton but different number of neutrons.

3. isotopes have different nucleon numbers but the same proton number.

4. Radioisotopes is isotopes with unstable nuclei.

5. Synthetic isotopes are produced by unstable nuclei that decay.

6. There are many uses of radioisotopes in the field of medicine, agriculture, industry and research.

7. Radioisotopes as used as tracers in scientific research, medical diagnosis and industry.