Two non-collinear parallel equal forces acting in opposite directions on a body
Select one:
a. Forms concurrent forces
b. Have zero effect on the body
c. Constitute a couple.
d. Keep the body at equilibrium
The correct answer and explanation is :
The correct answer is c. Constitute a couple.
Explanation:
In physics, a couple is a pair of forces that are equal in magnitude, parallel, and act in opposite directions, but are not collinear. These forces create a turning effect or torque, which causes rotational motion around a point (often referred to as the center of rotation or pivot point). A couple does not translate the body (i.e., it does not cause linear motion), but it can cause the body to rotate.
In the case presented, you have two non-collinear forces (forces that do not act along the same line), which are parallel and equal in magnitude but act in opposite directions. This setup creates a couple. The forces produce a net torque about any point that is not along the line of action of the forces. This torque causes the object to rotate, but there is no translational motion because the net force (the vector sum of the two forces) is zero.
Let’s break down why the other options are incorrect:
- a. Forms concurrent forces: Concurrent forces are forces that meet at a single point of action. In this case, the forces are parallel but not concurrent because they act in opposite directions and are not applied at a single point.
- b. Have zero effect on the body: While the net force on the body is indeed zero (because the forces are equal and opposite), the torque generated by the forces does not have a zero effect. The couple induces rotational motion, so there is an effect on the body.
- d. Keep the body at equilibrium: For an object to be in equilibrium, the vector sum of all forces and the sum of all torques (moments) must be zero. The forces in a couple produce a net torque, so they do not maintain equilibrium. Instead, they cause rotational motion unless balanced by another torque.
Thus, the correct description of two non-collinear, equal, and opposite forces acting on a body is that they constitute a couple, which causes rotational motion but not translational motion.