Why is it important to know the direction of the force applied to a moving object and the direction in which the object is moving when determining the work done on the object?

Work depends on the component of the force in the direction of the object's displacement: W = Fd cos θ, where θ is the angle between the force and the motion. Therefore, when the directions are at an angle, you must account for that angle using cosine. A perpendicular force does no work, while a force in the same direction as motion does positive work, so B, C, and D are incorrect.

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