Four particles, each with mass m, are arranged symmetrically about the origin on the x axis.A fifth particle, with mass M, is on the y axis.The direction of the gravitational force on M is:
A)$\uparrow$
B)$\downarrow$
C)$\leftarrow$
D)$\rightarrow$
E)"none of these directions"

Question

Four particles, each with mass m, are arranged symmetrically about the origin on the x axis.A fifth particle, with mass M, is on the y axis.The direction of the gravitational force on M is: 
A)$\uparrow$ 
B)$\downarrow$ 
C)$\leftarrow$ 
D)$\rightarrow$ 
E)"none of these directions"

Quizplus · Accepted Answer

The gravitational force on M will be in the direction towards the center of mass of the system, which in this case is the origin. Since M is on the y axis and the other four particles are symmetrically arranged on the x axis, the gravitational force will be pointing downwards, perpendicular to the x axis. Therefore, the correct direction is "F1F1F1S1F1F1F10".

Four Particles, Each with Mass M, Are Arranged Symmetrically About ↑\uparrow↑

Four Particles, Each with Mass M, Are Arranged Symmetrically About $\uparrow$