Complete Question
The complete question is shown of the first uploaded image
Answer:
Explanation:
The force vector acting upon the particle is [tex]\vec F[/tex] (The magnitude is F )
The displacement vector from point B to A is [tex]\vec L[/tex] (The magnitude is L )
Generally workdone is mathematically represented as
[tex]W_{BA} = \vec F * \vec L[/tex]
But from the question we are to that vector L has a magnitude L and makes and angle [tex]\theta \ radian[/tex] with the positive x-axis
also we are told that Force is pointing to the left and is parallel to the horizontal axis (i.e at angle [tex]\pi \ radian[/tex] (180°))
Generally the angle between the [tex]\vec F \ and \ \vec L[/tex] is [tex]\pi - \theta[/tex]
Hence the workdone is mathematically represented as
[tex]W_{BA} =F * L cos (\pi - \theta)[/tex]
=> [tex]W_{BA} =-F * L cos \theta[/tex]
Here the negative sign shows that the displacement is acting in opposite direction to the direction of the workdone (the force applied )
