When a book slides along a tabletop, the force of friction does negative work on it. Can friction ever do ?positive? work? Explain. (?Hint:? Think of a box in the back of an accelerating truck.)

Solution 16DQ Step 1 of 3: No, friction cannot do positive work. Step 2 of 3: As frictional force always resists the path of motion of the object. Since displacement of the object will be along the direction of motion. The frictional force always acts in the opposite to the direction of motion of object as it is resisting force. Therefore, the angle between the frictional force and displacement direction is =180 .0