Train A is moving at 100 kmh–1 through a station. Train B is also travelling at 100 kmh–1 through the station but in the opposit
e direction to train A. What is the speed of a seated passenger on? (a) train A relative to an observer on the station? (b) train A relative to another seated passenger on the same train? (c) train B relative to a passenger on train A?
(a) An observer on the station has a speed of 0 km/h. The speed of a passenger on Train A is 100 km/h. The relative speed is 100 km/h − 0 km/h = 100 km/h.
(b) The speed of both passengers is 100 km/h, in the same direction. The relative speed is 100 km/h − 100 km/h = 0 km/h.
(c) The speed of both passengers is 100 km/h, in opposite directions. The relative speed is 100 km/h − (-100 km/h) = 200 km/h.
<h3><em>Part 1-Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K.</em></h3><h3><em>Part 2-We can find giant stars in the upper part of the HR diagram, blue giants will be on the upper left corner since they have high luminosity and high temperature, while red giants will be on the upper right corner, having high luminosity but low temperature.</em></h3>
