A 50 kg student stands on a 4 kg skateboard at rest. The student catches a 9 kg backpack moving with a horizontal speed of 2 m/s in the direction the skateboard is free to roll. How fast will the student and the skateboard move after catching the backpack, assuming friction is negligible? Round your final answer to the hundredths place.​

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space? the cloud is extremely hot. the cloud is visible primarily because it reflects light from nearby stars. the cloud is cool and lies between you and a hot star. the cloud is cool and very dense, so that you cannot see any objects that lie behind it.