The hammering on a train track is often heard twice by workers farther down the track; first as the sound travels through the steel

and second as the sound travels through the air. This suggests which graph is true?

Radioactive decay of 40k atoms in an igneous rock has resulted in a radio of 25 percent 40k atoms to 75 percent 40Ar and 40Ca atoms. How many years old is this rock

If a negatively-charged rod is brought close to an electroscope that is negatively charged, what will the two leaves of the electroscope do? move closer together move farther apart not move at all become positively charged

In a certain state, electricity is generated by using Earth's heat. Wells are drilled and natural steam is taken out through pipes. This natural steam powers the generator and electricity is generated.

The age of fossils can sometimes be determined by radiometric dating. True or False

Two abiotic factor that effect an ecosystem are;

Rapid gas exchange can be accomplished more easily in air than in water because A. the O2 content of water is higher than that of air B. O2 diffuses more rapidly in water than air C. water is more dense and viscous D.

Which electron transition between the energy levels of hydrogen causes the emission of a photon of visible light?

According to a college survey, 22% of all students work full time. find the mean for the number of 3) students who work full time in samples of size 16.

How Much Potential Energy Does A 50kg block of Ice a Height of 4m Have?

In a summer storm the wind is blowing with a velocity of 8m/s north. Suddenly in 3 seconds, the winds velocity is 23m/s north. What is the winds acceleration?