A cyclist accelerates from rest at a rate of 7.0 m/s2. How long will it take the cyclist to reach a speed of 18 m/s? (Its really a subject for science, but I didn't want to put the wrong thing)

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  2 4/7 seconds

Step-by-step explanation:

Velocity and (constant) acceleration are related by ...

  v = at

Filling in the numbers, we can solve for t:

  18 m/s = (7 m/s²)·t

  t = (18 m/s)/(7 m/s²) = (18/7) s = 2 4/7 s

It takes the cyclist 2 4/7 seconds (about 2.57 seconds) to reach 18 m/s.

Comment on the subject

Problems involving position and its derivatives can reasonably be posted in the Math section. When energy or mass get involved, the Physics section is a better place. The relevant formulas for those are not always covered in algebra classes.

the answer is 8/21

hope this