Letter from a Concerned Parent Dear Mr. Chang, I am worried about your proposal to install a groundwater heating system in my daughter’s school. I don’t think that water at a temperature of 30ºC has enough energy to heat the school. If the school is too cold, the students won’t be able to focus on learning. Sincerely, David Li What do you think energy is?

True or false when elements combine to form a mixture, the resulting chemical properties may be very different from those of the elements that make it.

Aperson walks first at a constant speed of 4.89 m/s along a straight line from point a to point b and then back along the line from b to a at a constant speed of 2.95 m/s. what is the average speed over the entire trip?

22. the top of a cliff is located a distance h above the ground. at a distance h/2 there is a branch that juts out from the side of the cliff, and on this branch a bird's nest is located. two children throw stones at the nest with the same initial speed, one stone straight downward from the top of the cliff and the other stone straight upward from the ground. in the absence of air resistance, which stone hits the nest in the least amount of time?