Question

Two forces which cannot be replaced by a single equivalent force are said to form a ?

Answer 1

Answer:

From the definition of couple we came to know that couple is a pair of two parallel forces which acts in the opposite directions of each other.

Now,a couple can only produce rotational motion in a body and translational motion cannot be produced by a couple.

On the other hand, a single force will always produce translational motion in a body.

So, it's clear that the final result by a couple and a single force is completely different from each other.

That's why, a single equivalent force cannot replace a couple.