Перший раз хлопчик піднявся на свій поверх , а другий ліфтом. чи однакові роботи при цьому було виконано?

A = m * g * h => работа совершенная мальчиком и лифтом одинакова
N = A / t - мощность определяется еще и временем. на лифте мальчик доехал быстрее tл < tм => Мощность развиваемая лифтом больше мощности развиваемой мальчиком

При последовательном соединении полное сопротивление цепи равно сумме сопротивлений отдельных проводников, то есть R общ= 170 Ом

При последовательном соединении проводников сила тока во всех проводниках одинакова I3=I5.

I=U/R => I3=I5=120/170=0,71А(ампер)

При этом напряжение на любом резисторе равно произведению общего напряжения на отношение сопротивления резистора на общее сопротивление : U= Uобщ × R/ R общ.

U3= 120В×22/170 Ом =14,9 В

U5=120B ×10/170 Oм= 7, 06 В

Для кол-ва теплоты есть закон Джоуля-Ленца

Q=I^2× R ×t.

R1=120B×15/170 Om=10,59B

Q1= (0,71A)^2 × 10,59B ×1,5 минут= 8 Дж

Для мощности P= I^2×R

I6=0,71A

P6=0,71A^2×28 Om= 14,11 Bт

Для работы тока A=I^2× R× t

I7= 0,71A

A7=0,71A^2×75 Om ×1,5 минут =56,71 Дж

Nowadays people have started to realize that good health is very important, much more important than wealth. To be in good health people must follow a healthy life style, to do things that will help keep a healthy body and mind, to feel fit.There are several ways to do it. The state of your body depends on how much time you spend doing sports. At least everybody must do morning exercises every day. The healthiest kinds of sports are swimming, running and cycling. Healthy food is also a very important factor. The daily menu should include meat, fruit and vegetables, milk product, which are rich in vitamins, fat, proteins and etc. On the other hand modern diets are very popular especially among women. Diets may be harmful, if they are used in the wrong way. To be healthy, people should get rid of their bad habits. It’s necessary to stop smoking and drinking much. Everyone should remember that cigarettes, alcohol and drugs destroy both body and brain. In addition it is recommended to watch TV less, avoid anxiety and observe daily routine. )

1)Good health is very significant.          

2)All diets are useful and healthy.          

3)It is recommended to do yoga to be in good health.      

4)Alcohol and cigarettes influence only on body.          

5)It is important to get rid of bad habits in order to keep a healthy body and mind.          

Объяснение: