What is the average speed shown on the graph between point A and point D?

5/3 m/s or

6 km/h

Explanation:

really ? the average speed is just the straight connection in the graph from A to D.

that means the travel time was 40-10 seconds = 30 seconds.

and the distance traveled was 60-10 = 50 meters.

so, the average speed was

50 meters / 30 seconds

to bring this to standard m/s

5 m / 3 s = 5/3 m/s

or to standard km/h

an hour has 60 minutes or 120 30-seconds intervals

50 m/ 30 s × 120/120 = 6000 m / h = 6 km/h

absorption lines are where light has been absorbed by the atom thus you see a dip in the spectrum whereas.

emission spectra have spikes in the spectra due to atoms releasing photons at those wavelengths.

explanation: