At a construction site a pipe wrench struck the ground with a speed of 31 m/s. (a) From what height was it inadvertently dropped? (b) How long was it falling?

Much easier if you work the questions in the reverse order.

b). Time = v/g

31m/s / 10m/s^2 = 3.1 seconds

a). Average speed during the fall = (1/2)(0+31m/s) = 15.5 m/s

Distance = (average speed) (time)

(15.5 m/s) (3.1 sec) = 48.05 meters

dopamine..

"it was found that some people who were taking the drug l-dopa to raise their levels of dopamine were developing schizophrenic-like symptoms supporting research a strength of the dopamine hypothesis is that there are many studies which have shown support for the neurochemical explanation."

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.