Final answer:
The portion of the force that does work when pulling an object horizontally is the horizontal component of that force. Work is calculated as the product of this horizontal force component and the displacement in the horizontal direction.
Step-by-step explanation:
When you pull an object horizontally, the part of your force that does work is the component that is in the same direction as the displacement of the object. According to the work-energy theorem, the work done on an object is the scalar product of the force applied and the displacement (W = F . d). If the applied force is at an angle, only the horizontal component of the force contributes to the work done on the object. In other words, work is the product of the force's horizontal component (Fx = F cos θ) and the horizontal displacement (d), where θ is the angle between the force and the horizontal direction (W = Fx * d).
For the given example, if a person pulls a lawn mower with a force at an angle to the horizontal direction, we would calculate the work done using the horizontal component of that force. If the person were to pull the mower with the same force but entirely in the horizontal direction, the work done would be calculated as the product of the magnitude of the pulling force and the distance moved by the mower (W = F * d).