A student practicing for a track meet ran 250 m in 30 sec

v= 8.3 m/ s^-1

Explanation:

S=vt

v= S/t

v= 250 m/ 30 s

v= 8.3 m/ s^-1

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:

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."