2. (a) (3 points) Given the vector valued function r(t) describing the position of an object (in meters), what physical quantity does F(t) describe? What are the units? (b) (3 points) What physical quantity does | r"(t) | describe? What are the units? (c) (4 points) Explain why the unit tangent vector has no units. What does it describe? (d) (3 points) Find the unit tangent vector for the function r (t) = (t2, At, 4 In(t)). (e) (4 points) Find the equation of the line tangent to F (t) at t = 1