A scientist in Northern California is studying the tree rings of a very old redwood tree. He notices that the oldest tree rings are very narrow. As the rings move away from the center, he observes 15 rings that get wider and wider. What can you determine about the climate during the 15-year period during which the tree rings grew wider?

The climate was warmer and wetter.
The climate was warmer and drier.
The climate was colder and drier.
The climate was colder and wette

When an object is heated it contracts. a. true b. false

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?