Polyester are commonly made up of an organic alcohol that contains a hydroloxyl and a carboxylic acid which contains a carboxyl. polyester is a class of synthetic polymers built up from multiple chemical repeating units linked together by ester groups. it also displays a wide array of properties and practical applications.
Answer:
51.96 years
2) 30 million of years
Explanation:
First we must know the travel time of the ship seen from the earth. The spaceship travels at half the speed of light, this means that the amount of time the spacecraft must spend to travel the same distance is double compared to the light, that is 60 years.
Now due to the speed of the ship, we must take into account relativistic effects, such as time dilation, this is given by:
Where t is the time measured in the ship, t' is the time measured in the earth, inertially moving with velocity v.
Rewriting for t:
This is the amount of time it would take you reach the Whirlpool galaxy in the spaceship.
2) a light year is a measure of distance, which indicates the kilometers that light travels in a year. Thus, the light emitted by Whirlpool galaxy takes 30 million of years reaches our planet.
frictional force that air exerts against a moving object
Given: The number = 0.0069 that has to be expressed in scientific notation
.
Concept: When we express any number in scientific notation then we shall consider two points.
(i) If we shift the decimal point from left to right after first (non-zero) digit then we count the number of shifted place of decimal and write them in terms of the negative power of 10. For example, 0.004789 = 4.789 ×10⁻³
(ii) If we shift the decimal point from right to left after first (non-zero) digit from the left end then we count the number of shifted place and write then in terms of the positive power of 10. For example, 4789.24 = 4.78924 ×10⁺³ = 4.78924 ×10³
Now, we shall convert the given number 0.0069 in scientific notation
.
0.0069 = 6.9 ×10⁻³ because we have shifted the decimal from left to right for three places that is after digit 6.
Hence, the last option 6.9 ×10⁻³ will be the correct option.
