Ablock with a weight of 3.00 n is at rest on a horizontal surface. a 1.00 n upward force is applied to the block by means of an attached vertical string. collapse question part step 1 how many forces act on the block?

Initially, when the block is at rest on the horizontal surface, two forces act on the block:
- its weight (3.00 N) acting downward
- the vincular reaction of the surface, acting upward and with same magnitude of the weight (3.00 N)

After the force of the vertical string starts to act on the block, three forces act on the block:
- its weight (3.00 N) acting downward
- The tension of the string, acting upward a force of 1.00 N
- the vincular reaction of the surface, acting upward but with less intensity than before: in fact, it counterbalances the net force acting upward, which is now (1.00N-3.00 N=-2.00 N), so the vincular reaction now is 2.00 N.