What conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

Agirl throws a ball. if the ball's acceleration is 12 m/sec/sec and its mass is 0.5 kg, how much force did the girl apply to the ball?

You add 800 ml of water at 20c to 800 ml of water at 80c what is the most likely final temperature of the mixture ? a. 100c b. 60c c. 25 c d.50c

Does the distance travelled by an oscillating mass between times t=0 and t2 equal the displacement of the particle over the same time period if t2> t/2? hint: consider a sine wave starting at t1=0, then consider a closing wave starting at t1=0, for your explanation.