A constant force of 15 N in the negative y direction acts on a particle as it moves from the origin to the point
m.How much work is done by the given force during this displacement?
A)+45 J
B)−45 J
C)+30 J
D)−30 J
E)+75 J

Question

A constant force of 15 N in the negative y direction acts on a particle as it moves from the origin to the point 
m.How much work is done by the given force during this displacement?
A)+45 J 
B)−45 J 
C)+30 J 
D)−30 J 
E)+75 J

Quizplus · Accepted Answer

The work done by a force is given by the dot product of the force and displacement vectors. In this case, the force is constant and in the negative y direction, so its vector form is F = (0,-15,0) N. The displacement vector is (11,0,0) m. The dot product of these vectors is:
W = F · d = (0,-15,0) · (11,0,0) = 0 + (-15) + 0 = -15 J
Since the force is acting in the opposite direction to the displacement, the work done is negative. Therefore, the best choice is B) -45 J.

A Constant Force of 15 N in the Negative Y