If humans originated in africa and migrated to other parts of the world some time would be required for this to occur. at the modest rate of one kilometer per year, how many centuries would it take for humans originated in africa to travel to china, some 10,000 kilometers away?

Asled is being held at rest on a slope that makes an angle θ with the horizontal. after the sled is released, it slidesa distance d1 down the slope and then covers the distance d2 alongthe horizontal terrain before stopping. find the coefficient ofkinetic friction μk between the sled and the ground, assumingthat it is constant throughout the trip. find the coefficient of kinetic frictionμk. express your answer in terms of someor all of the variables d1, d2, and θ.

How do cracks affect the rate of weathering?

Give an example of how both short term and long term memory are involved. explain procedural, semantic ,and episodic memory and then how each is involved in this