Review | Constants For those students not familiar with the concept of efficiency, it is simply the work done divided by the energy expended (multiply by 100 to get the efficiency in percent). This is the first in a series of questions concerning power output in several forms: by humans, by car engines, and by hydroelectric power plants. Power of a Human Running Up Stairs A 57.0-kg woman takes 4.270 seconds to run to the top of the spectator stands at her local high school track. The top of the stands are 4.90 m above the level of the track from which she starts. Ignore air resistance during the climb. The runner starts and ends her climb at rest. As a preliminary exercise, make a free-body diagram for the runner during her climb. For the purpose of this diagram, simplify the situation by replacing the spectator stands with a ramp. Notice that only the height of the stands was given, because only the altitude change is needed for the energy calculation; but for these preliminary questions concerning forces, assume a ramp of length 9.80 m (measured along the ramp). Human locomotion is complex, but we would like to treat the runner as a particle; so draw the runner with one foot on the ramp directly under the runner's center of mass (the other foot will be off the ground at this instant). Since the runner starts and ends at rest, she must first speed up and then slow down, but draw the free-body diagram for an instant when she has a constant velocity up the ramp. Part A What are the normal and the frictional components of the force on the runner by the ramp at this instant when her velocity is constant? Assume that Away from the Ramp is the positive direction for the normal component, and that Up the Ramp is the positive direction for the frictional component. Give your answer as an ordered pair, with the normal component first, followed by a comma, followed by the frictional component. View Available Hint(s) IVO AEd normal component, frictional component = 551.91,86.16 N, N Submit Previous Answers X Incorrect; Try Again; 4 attempts remaining