A meter stick on a horizontal frictionless table top is pivoted at the 80-cm mar

Question

A meter stick on a horizontal frictionless table top is pivoted at the 80-cm mark. A force F1 is applied perpendicularly to the end of the stick at 0 cm, as shown. A second force F2 (not shown) is applied perpendicularly at the 100-cm end of the stick. The forces are horizontal. If the stick does not move, the force exerted by the pivot on the stick:

A. Must be Zero

B. must be in the same direction as F1 and have magnitude of |F1|-|F2|

C. must be directed opposite to F1 and have magnitude of |F1|-|F2|

D. must be in the same direction as F1 and have magnitude of |F1|+|F2|

E. must be directed opposite to F1 and have magnitude of |F1|+|F2|

What does it mean "the forces are horizontal" and "the force exerted by the pivot"?

I would need the answer to the question and also the explanation. Thanks!

Explanation / Answer

Pivot is a joint, which restricts the motion of an object.

There are various kind of joints, which govern the direction of the force on the object by the joint.

Here when it says that the force are horizontal it means that pivot is capable of applying only horizontal force on the rod and no vertical force.

There is no external horizontal force and hence force by pivot = zero (A)

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