A runner completes a 400-meter race in 2.5 mins. What is the runner's average speed?

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.

Displacement is the slope of a velocity vs. time graph a. true b. false

What is true for a substance that releases energy