For those wanting to answer the question: "How long would it take for me to fall through the earth assuming it was in a vacuum?", the Minute Physics Channel on You Tube has an answer. The math on some of the problems may be a bit daunting but the visuals are good and it is easy to understand some fairly difficult concepts. It also has some practical applications. Is it better to walk or run through the rain if you want to be less wet?
Terminal velocity is reached when the force of acceleration equals the force of resistance in the form of drag. Gravity produces an acceleration of 9.8 meters/second/second or 9.8 meters/second squared.
Acceleration due to gravity - 1 min.
Objects regardless of mass fall at the same rate due to gravitational acceleration assuming that the resistance of drag is the same for both objects.
Speed is a scalar quantity in distance per unit of time without specifying direction. Velocity is a vector quantity in distance per unit of time with a direction.
Examples.
Speed: A car travels 40 miles per hour.
Velocity: A car travels 40 miles per hour traveling south.