Amountain is 1100 feet above sea level. a trench is 420 feet below sea level. what is the difference in elevation between the mountain top and the bottom of the trench?

With i really need the correct answer!

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

The force needed to overcome static friction is usually less than that needed to overcome kinetic friction.true or false?