What did the early plants add to the atmosphere and why was that important? what else did they create?

Because light travels in a straight line and casts a shadow, isaac newton hypothesized that light is

The uniform slender bar rests on a smooth horizon- tal surface when a force f is applied normal to the bar at point a. point a is observed to have an initial acceleration aa of 20 m/s2, and the bar has a corre- sponding angular acceleration of 18 rad /s2. deter- mine the distance b.

You've already seen the value of 9.8 in this lesson. what's this value called? what quantity does it represent?