
Answer:
a)  v = 7.69 10³ m / s,  b)   T = 92.6 min
Explanation:
a) For this exercise we use the centripetal acceleration ratio, which in itself assumes a circular orbit, is equal to the acceleration of gravity
     a = v² / r
     v = [tex]\sqrt{a r}[/tex]
the distance to the ISS is
      r = R_earth + d
      r = 6400 10³ + 400 10³
      r = 6800 10³ m
we calculate
      v = [tex]\sqrt{8.69 \ 6800 \ 10^3}[/tex]Ra (8.69 6800 103)
      v = [tex]\sqrt{59.09 \ 10^6}[/tex]
      v = 7.687 10³ m / s
     Â
the result with the correct significant figures
      v = 7.69 10³ m / s
b) The speed of the ISS is constant, so we can use the uniform motion relationships
      v = d / t
if distance is the orbit distance
      d = 2π r
time is called period
      v = 2π r / T
      T = 2π r / v
let's calculate
      T = 2π 6800 10³ /7,687 10³
      T = 5.558 10³ s
let's reduce the period to minutes
      T = 5.558 10³ s (1 min / 60s)
      T = 9.26 10¹ min
      T = 92.6 min