29. Сформулируйте вопросы на английском языке и дайте ответы на них. Какие условия накладываются на законы сохранения в физике? Какие данные можно извлечь из экспериментов в механике?

What conditions are imposed on conservation laws in physics?

In physics, the law of conservation of energy states that the total energy of an isolated system cannot change—it is said to be conserved over time. Energy can be neither created nor destroyed, but can change form, for instance chemical energy can be converted to kinetic energy in the explosion of a stick of dynamite.

A consequence of the law of conservation of energy is that a perpetual motion machine of the first kind cannot exist. That is to say, no system without an external energy supply can deliver an unlimited amount of energy to its surroundings.

What data can be taken from experiments in mechanics?

‘In the matter of physics, the first lessons should contain nothing but what is experimental and interesting to see. A pretty experiment is in itself often more valuable than twenty formulae extracted from our minds.’ - Albert Einstein

‘Experimental mechanics’ can be defined as the investigation by experimental means of the mechanical behaviour of engineering systems subjected to load. Experimental mechanics approaches that provide a measure related to the strain are therefore very important design tools. Many of these techniques have been available for decades but recently have been gaining popularity because of the advances in computing power and decreasing hardware costs. More importantly from the design perspective, the necessity for experimental data to validate numerical models of systems manufactured from complex nonlinear inhomogeneous materials, such as fibre reinforced polymer composites, is ever increasing. Experimental mechanics approaches have much to offer and it is the purpose of this module to provide an overview of the range of application and operation of the techniques.

30. Сформулируйте вопросы на английском языке и дайте ответы на них. Чем обусловлено уменьшение и увеличение величины, если она прямо (обратно) пропорциональна некоторой известной величине? Что определяет первая производная от функции одной переменной?

What cause the decrease or increase in value if it is directly (inversely) proportional to a known value? What determines the first derivative of the function of one variable?

Increase or decrease in value cased by proportionality to known value. For example, let’s take Newton’s second law. Acceleration is directly proportional to force and inversely proportional to the mass of body. It means that if mass is constant and force is increasing, we will take increasing value of acceleration because 10,100,1000 N over 10 kg in first situation equal 1, in second 10 and 100 m/s² in third, and vice versa if acting force is constant and mass is growing, we will take decreasing value of acceleration.

First derivative of the function of one variable determines rate of changing of the function.