Which scientific phenomenon helps scientists determine the chemical composition of some stars? A.
absorption of light in a star’s atmosphere
B.
dispersion of light as it enters Earth’s atmosphere
C.
reflection of light
D.
refraction of light

answer;

18.5 seconds

explanation;

velocity is distance covered per unit time; it is given by displacement divided by time.

thus; time = displacement/velocity

total time = total displacement/velocity

total distance = 5000 meters south

total time = 5000/4.5

                  = 1111.11 seconds

but; 1 minute = 60 sec

thus; 1111.11 /60

                = 18.51 seconds

thus; the time taken is 18.5 seconds