If two forces act together on an object then the magnitude of the resultant is least when the angle between the forces is:

Explanation

The correct option is (c) - when two forces act together on an object and the angle between them is 180°, the magnitude of the resultant force is least. Now, let's explain each option: (a) 60°: When the angle between the forces is 60°, the magnitude of the resultant force will be greater than when the angle is 180°. This is because the forces have a component in the same direction, adding up to a larger magnitude. (b) 90°: When the angle between the forces is 90°, the magnitude of the resultant force will be greater than when the angle is 180°. This is because the forces are acting at right angles to each other, resulting in a larger magnitude for the resultant force. (c) 180°: When the angle between the forces is 180°, the magnitude of the resultant force is least. This is because the forces are acting in opposite directions, canceling each other out to some extent. (d) 360°: When the angle between the forces is 360°, it is the same as having no angle between them. In this case, the magnitude of the resultant force will be the sum of the magnitudes of the individual forces. In summary, when two forces act together on an object, the magnitude of the resultant force is least when the angle between the forces is 180°.