Which of the following types of spectra have dark lines?

a. emission spectra

b. absorption spectra

c. continuous spectra

d. noncontinuous spectra

Dan is gliding on his skateboard at 4.0 m/s. He suddenly jumps backward off the skateboard, kicking the skateboard forward at 8.0 m/s. How fast is Dan going as his feet hit the ground? Dan's mass is 50 kg and the skateboard's mass is 5.0 kg?

A hypothesis is? close agreement by competent observers of observations of the same phenomena. a guess that has been tested over and over again and always found to be true. an educated guess that has yet to be proven by experiment.

A pendulum is designed to transfer potential gravitational energy into: a. Kinetic energy c. Joules b. Elastic potential energy d. Watts

A ship leaves a harbor and sails at 23.5 ∘ to the north of due west. After traveling 575 km, how far west is the ship from the harbor?

if a material has a half-life of 24 hours, how long do you have to wait until the amount of radioisotope is 1/4 its original amount?

White moths were found in huge numbers in the city of Birmingham. These moths could be easily camouflaged by the trees. Because of sudden industrial development, the trees in the city were covered with soot.

What two factors determine how fast weathering occurs

A sound that's produced by a single wave at a constant frequency and with no overtones is called

Which of the following is ignored when determining the relative mass of atoms? protons nucleus electrons. neutrons

Gamma radiation can be significantly reduced by ... A sheet of paper Air A 3 mm thickness of aluminium Several cm of lead