text: i need help with science homework....help, please? here are some questions.  1.  in a amusement park ride, a girl stands with her back agaist the inside wall of a circular room.  the room begins to whirl around.  after the room reaches a constant speed, the floor drops down, but she doesn't fall.  identify three forces acting on her and give the direction of each.   2.  a book is sitting on the dashboard of a car that is stopped at a traffic light.  as the car starts to move forard, the book slides backward off the dashboard. use the term interia to explain what happened.   3.  compare the effects of ravity and air resistance on a falling skydiver before and after she opens her parachute. 1. gravity is acting straight down, centrifugal force is acting towards the wall, and friction is holding her against the wall.  obviously the centrifugal force and friction together are stronger than the gravity, or she would fall.  2. the book was "at rest" -- an object tends to stay at rest unless acted on by an external force (that's inertia).  the book's mass (weight) gave it enough inertia to overcome the friction with the dashboard, so when the car moved the book didn't move with it, but tried to stay where it was.  3. the surface area of the skydiver before opening the parachute doesn't offer much air resistance, so the skydiver is mostly being acted on by gravity and reaches terminal velocity fairly quickly.  once the parachute is opened, the surface area of the skydiver/parachute combination is many times greater than it was, greatly increasing air resistance -- which slows the acceleration due to gravity enough to allow the skydiver to make a soft landing.  :)