30. A plane heads 10 at 150 mi/h. It experiences a 30 mi/h crosswind blowing 50 . What is the ground speed of the plane? What is the plane's direction of movement relative to the ground? (Round all values to 2 decimal places.)

31. A swimmer is swimming 2.5 mi/h (relative to the water) across a straight river flowing east at 0.7 mi/h. In what direction should the swimmer head in order to arrive at a landing point that's due south of her?

32. A calculus book is on a ramp that is inclined 15 to the horizontal. If the calculus book weighs 1375 lbs, find the magnitude of the force required to keep it from sliding down the ramp (ignoring friction). Also, find the magnitude of the force experienced by the ramp due to the weight of the calculus book.

33. A 15000-lb tractor is on a hill. If a force of 2000 lbs is just sufficient to keep the tractor from rolling down the hill, find the angle of inclination of the hill. (Assume no friction on the hill.)