Mechanics and Motion

Motion is one of the key topics in physics. Everything in the universe moves. It might only be a small amount of movement and very very slow, but movement does happen. Don't forget that even if you appear to be standing still, the Earth is moving around the Sun, and the Sun is moving around our galaxy. The movement never stops. Motion is one part of what physicists call mechanics. Over the years, scientists have discovered several rules or laws that explain motion and the causes of changes in motion. There are also special laws when you reach the speed of light or when physicists look at very small things like atoms.

Speed it Up, Slow it Down

The physics of motion is all about forces. Forces need to act upon an object to get it moving, or to change its motion. Changes in motion won't just happen on their own. So how is all of this motion measured? Physicists use some basic terms when they look at motion. How fast an object moves, its speed or Velocity, can be influenced by forces. (Note: Even though the terms 'speed' and 'velocity' are often used at the same time, they actually have different meanings.)

Acceleration is a twist on the idea of velocity. Acceleration is a measure of how much the velocity of an object changes in a certain time (usually in one second). Velocities could either increase or decrease over time. Mass is another big idea in motion. Mass is the amount of something there is, and is measured in grams (or kilograms). A car has a greater mass than a baseball.

Simple and Complex Movement

There are two main ideas when you study mechanics. The first idea is that there are simple movements, such as if you're moving in a straight line, or if two objects are moving towards each other in a straight line. The simplest movement would be objects moving at constant velocity. Slightly more complicated studies would look at objects that speed up or slow down, where forces have to be acting.

There are also more complex movements when an object's direction is changing. These would involve curved movements such as circular motion, or the motion of a ball being thrown through the air. For such complex motions to occur, forces must also be acting, but at angles to the movement.

In order to really understand motion, you have to think about forces, acceleration, energy, work, and mass. These are all a part of mechanics.

Motion Glossary and Terms

 

Motion Glossary and Terms

Acceleration - Acceleration is the measurement of the change in an object's velocity. It is equal to the change in velocity over the change in time. Acceleration is a vector. 

Collision - A collision in physics occurs when any two objects bump into each other. 

Displacement - In physics, displacement refers to an object's overall change in position. It is a vector quantity.

 Energy - Energy is the ability to do work. The standard unit of measure for energy is the joule. 

First law of motion - The first law of motion states that any object in motion will continue to move in the same direction and speed unless external forces act on it.

 Force - Force is the measurement of a push or pull on an object. Force is a vector measured in newtons.

 Friction - Friction is the resistance of motion when one object rubs against another. It is a force and is measured in newtons.

Gravity - Gravity is a force caused when the mass of physical bodies attract each other. On Earth gravity pulls at objects with an acceleration of 9.8 m/s2. 

Impulse - An impulse is a change in momentum. 

Joule - The joule is the standard unit of measure for energy and work. 

Kinetic energy - Kinetic energy is the energy an object has due to its motion. It is a scalar quantity calculated using the formula KE = ½ * m * v2, where m = mass and v = velocity.

Mass - Mass is a measurement of how much matter is in an object. It is usually measured in kilograms. 

Momentum - Momentum is a measurement of mass in motion. Momentum is equal to the mass times the velocity of an object. It is a vector measured in newton-seconds. 

Newton - The newton is the standard unit of measure for force. Pascal - The pascal is the standard unit of measure for pressure. 

Potential energy - Potential energy is the energy stored by an object due to its state or position. It is measured in joules. Power - Power is a measurement of the rate at which energy is used. Power is calculated by dividing work over time. The standard unit for power is the watt. 

Pressure - Pressure is the force over a given area. Pressure is measured in pascals. 

Scalar - A scalar is a measurement that only measures the magnitude. Unlike a vector, a scalar does not have direction. Second law of motion - The second law of motion states that the greater the mass of an object, the more force it will take to accelerate the object. 

Simple machine - A simple machine is a basic mechanical device for applying a force and doing work. Some examples of simple machines include the lever, pulley, inclined plane, wedge, and screw. 

Speed - Speed is the measurement of how fast on object moves relative to a reference point. It is a scalar quantity measured by distance over time. 

Third law of motion - The third law of motion states that for every action there is an equal and opposite reaction. 

Vector - A vector is a quantity that has both a magnitude and a direction. 

Velocity - Velocity is the rate of change in an object's position. Velocity is a vector quantity. The magnitude of velocity is the object's speed. 

Watt - The watt is the standard unit of measure for power. Weight - Weight is the force of gravity on an object. In physics, weight is measured in newtons. 

Work - Work occurs in physics when a force acts on an object to move it some distance. Work is equal to the force times the distance and is measured in joules.

                                                 How to talk about Sickness?

 

 

                                                   Stop Saying - I Don’t Know

What Is Time?

 WHAT IS TIME?

Time is familiar to everyone, yet it's hard to define and understand. Science, religion, philosophy, and the arts have different definitions of time, but the system of measuring it is relatively consistent.Clocks are based on seconds, minutes, and hours. While the basis for these units has changed throughout history, they trace their roots back to ancient Sumeria. The modern international unit of time, the second, is defined by the electronic transition of the cesium atom. But what, exactly, is time? Physicists define time as the progression of events from the past to the present into the future. Basically, if a system is unchanging, it is timeless. Time can be considered to be the fourth dimension of reality, used to describe events in three-dimensional space. It is not something we can see, touch, or taste, but we can measure its passage. 

Physics equations work equally well whether time is moving forward into the future (positive time) or backward into the past (negative time.) However, time in the natural world has one direction, called the arrow of time. The question of why time is irreversible is one of the biggest unresolved questions in science.

One explanation is that the natural world follows the laws of thermodynamics. The second law of thermodynamics states that within a closed system, the entropy of the system remains constant or increases. If the universe is considered to be a closed system, its entropy (degree of disorder) can never decrease. In other words, the universe cannot return to exactly the same state in which it was at an earlier point. Time cannot move backward.As far as the universe is concerned, time had a beginning. The starting point was 13.799 billion years ago when the Big Bang occurred. We can measure cosmic background radiation as microwaves from the Big Bang, but there isn't any radiation with earlier origins. One argument for the origin of time is that if it extended backward infinitely, the night sky would be filled with light from older stars.

Will time end? The answer to this question is unknown. If the universe expands forever, time would continue. If a new Big Bang occurs, our time line would end and a new one would begin. In particle physics experiments, random particles arise from a vacuum, so it doesn't seem likely the universe would become static or timeless. Only time will tell.

Где найти друга по переписке

 

Где найти друга по переписке: 4 лучших сайта

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Writing a good CV

When you're applying for a job, a great CV is essential. Find out what to include and what to avoid for the best chance of getting an interview.

When you're looking for work, you need an attractive, clear and memorable CV (curriculum vitae) that shows your potential employer all the skills and experience you have for the job.

What should you include in a CV?

This article mainly focuses on writing a UK-style CV. If you're applying for a job internationally, be aware that the standard length, format and tone can vary from country to country. It's a good idea to check the expected format in the country or company you're applying to. 

Contact details 

Make sure the potential employer has a way of contacting you. Include your full name, telephone number and email address. 

Photo?

In many countries, employers expect to see a professional-looking photo on a CV. In others, like the UK, Canada and the USA, the law prohibits employers from asking for a photo, and it is better not to include one. Try to find out if it is usual to include a photo in the working environment you're applying to.

Education

List and date the most important qualifications you have obtained, starting with the most recent. You can also include any professional qualifications you have.

Work experience

List and date the jobs you've had and the companies you've worked for, starting with the most recent. It's usually enough to cover the last ten years of your work history. Include your job title, responsibilities and achievements in the job. 

If you have a lot of work experience, give the job titles but be selective about which responsibilities and achievements you highlight. Reduce the detail about jobs that are less relevant to the role you're applying for and draw attention to the most important experience you bring.

Skills 

These could include the languages you speak, the computer programs you can use well, the class type of your driving licence and any other professional skills you might have that are relevant to the job you're applying for.

Eight useful tips

Before you start getting ready to list your qualifications and work experience, here are eight useful tips to think about.

1. Keep it short … but not too short!

Your CV should be one to two sides of A4 paper. If you find you've got too much information, summarise and select the most relevant points. If it's shorter than a page, consider including more information about your skills and the responsibilities you had in your previous roles.

2. Use active verbs.

When you describe what you have achieved in previous jobs, use active verbs for a strong positive effect on the reader. For example, to make a change from was responsible for, use verbs like led or managed (a team / a project); created or developed (a product / a positive atmosphere); delivered (results/training); and provided (support/training). 

3. Fill in the gaps.

Avoid leaving gaps in your employment history. If you were travelling the world, on maternity leave or looking after small children, include that in your CV.

4. Make sure it's up to date.

Always ensure your CV is up to date. Include your most recent experience at the top of each section.

5. Don't exaggerate or lie.

Your potential employer can easily check information about where you have studied and worked. Don't be tempted to lie or exaggerate about your expertise, because sooner or later this will be discovered and may result in you losing the job. 

6. Spend time on the layout.

Make sure your CV is clear and easy to read. Use bullet points and appropriate spacing, keep your sentences short, line up your lists neatly and use a professional-looking font (e.g. Arial font size 12). 

7. Check for mistakes.

Mistakes on a CV create a bad impression. Use spell check, reread your CV and ask someone else to check it for you too before you send it.

8. Include a cover letter.

When you send your CV to apply for a job, you should send it with a cover letter or email to introduce your application. The cover letter should show your personal interest in the role, highlight the skills and experience you bring and encourage the employer to read the attached CV. 

Writing a good CV takes time and is hard work, but these tips and your effort will help you get the best possible start in your job search. Good luck!