試題詳解

4. Jack is pushing a box moving at a constant speed on a horizontal ground. Due to friction between the box and the ground, Jack has to continue to do positive work to keep the box moving, and the work output per unit time is P. If Jack would like to push the box along a slope of an inclined angle of 18 degrees (relative to the horizontal ground) at the same constant speed, make an estimate of the power output required. Assume the coefficient of the kinetic friction remains the same and equals unity.
(A) P
(B) 1.26P
(C) 1.33P
(D) 1.42P

(E) 1.51P