Sample Problem 2 A woman pushes a trunk on a railway platform which has a rough surface. She applies a force of 100 N over a distance of 10 m. Thereafter, she gets progressively tired and her applied force reduces linealry with distance to 50 N. The total distance through which the trunk has been moved is 20 m. Frictional force is 50 N versus displacement. The work done by the two forces over 20 m is (d) -1000 / (a) -25 / (b) -50 / (c)-100/