Question

1. what is lubricant ? how does a lubricant reduce friction ?
2. why is friction called a necessary evil?
3. what are the changes occur during adulescence ?
4. A girl is 11 years old and 125cm tall . find her height at the end of the growth period using the formula ?​

Answer 1

$\huge\fbox\red {˙❥answer}$

1. Lubrication reduces the heat generated when two surfaces are in motion. It smoothes the process by forming a film between two surfaces that reduces friction and thus improves performance and efficiency. There are different variety of lubricants and oils available such as Engine Oil, Hydraulic Oil, and Greases.
2. Frictional force causes a lot of losses in general upkeep and wear and tear of machinery. Hence it is considered as a evil. But almost all crucial tasks cannot be carried out without the presence of friction. ... Hence it is considered as a necessary evil .
3. An adolescent may grow several inches in several months followed by a period of very slow growth, then have another growth spurt. Changes with puberty (sexual maturation) may happen gradually or several signs may become visible at the same time.

Answer 2

1. what is lubricant ? how does a lubricant reduce friction ?

A lubricant is a substance which helps to reduce friction and to make a machine or a body move smoothly.

A lubricant reduce friction by making the body oily by which it can slide.

2. why is friction called a necessary evil?

As due to friction much energy is wasted by making a body or a machine work.

It is necessary, not necessary but compulsory because it helps to do the work.

3. what are the changes occur during adulescence

Many changes such as pimples, acnes, in boys sperms use to form and in girls eggs starts forming.

4. A girl is 11 years old and 125cm tall . find her height at the end of the growth period using the formula ?

Present height/% of full height at this age×100

=125/88×100

=142cm Ans

please mark as BRAINLIEST