What is the name of the line drawn perpendicular to the surface where a light ray strikes?

How is the gravitational force related to the distance between two objects?

Use the profile illustrated for problem (1). assume that the layer of silty sand fill (sm) is placed over the entire site. estimate the thickness of the fill (h - in feet) that will cause the effective vertical stress at the center of the clay layer to increase by 517.5 pounds per square foot.

Calculate a pendulums frequency of oscillation (in hz) if the pendulum completes one cycle in 0.5s.