I've got an energy and work problem. the premise of the problem is: a crate with a mass of m is on a ramp that is inclined at an angle of 30° from the horizontal. a force with a magnitude of f directed parallel to the ramp is used to pull the crate with a constant speed up the ramp a distance of d. there are a set of subquestions and i've answered them as best as i can, but i don't think i'm right. could someone give me the answers and me understand why i'm wrong? 1. what is the work done on the crate by the applied force f? --i said cos30 * f * displacement 2. 2. what is the work done on the crate by the gravitational force exerted on the crate by earth? --i said m*9.8*tan30 3. what is the work done on the crate by the normal force, with a magnitude of fn, exerted on the crate by the ramp? (hint: recall that the normal force is perpendicular to the surface of the ramp.) --i said zero 4. what is the work done on the crate by the frictional force fk? --i don't understand this one 5. what is the total force acting on the crate? --i said f, as in the pre-defined force 'f' 6. what is the work done on the crate by the total force? --i don't understand how this is different from the first one