Which statement is true about vectors? a. All quantities in physics are not vectors.

b. Avector may have either magnitude or direction.

c. The vector's length should be proportional to its magnitude.

d. Two vectors can be added only if they have the same direction.

Awater slide of length l has a vertical drop of h. abby's mass is m. an average friction force of magnitude f opposes her motion. she starts down the slide at initial speed vi. use work-energy ideas to develop an expression for her speed at the bottom of the slide. then evaluate your result using unit analysis and limiting case analysis. express your answer in terms of the variables h, m, l, vi, f and appropriate constants. vf v f