There are three forces F1, F2, and F3 acting on a body, all acting on a point P on the body. The body is found to move with uniform speed.
(a) show that the forces are coplanar
(b) show that the torque acting on the body about any point due to these three forces is zero
(a) Acceleration of the body is zero as the three forces F1, F2, and F3 on a point on a body has a resultant force equal to zero. The direction of forces F1 and F2 are in
the plane of the paper and in their sum is in the opposite direction in the same plane. Also, F3 is in the same plane. Therefore, all the three forces are coplanar.
(b) The resultant of forces F1, F2, and F3 are zero and the torque is also equal to zero. That is, the resultant force is given as:
F = F1 + F2 + F3 = 0.
Therefore, it can be said that at any point the torque acting will be zero.