Cindy runs 2 kilometers every morning. she takes 2 minutes for the first 250 meters, 4 minutes for the next 1,000 meters, 1 minute for the next 350 meters, and 3 minutes for the rest.
cindy’s average speed for the entire run is __ meters per minute. one kilometer is the same as 1,000 meters.
hint: average speed = total distance/total time

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."

resonant frequency

grav forces affect all objects magnetic forces affect magnetic objects and electric currents

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.