A 15.0 lb block rests on the floor. (a) What force does the floor exert on thebl

Question

A 15.0 lb block rests on the floor. (a) What force does the floor exert on theblock?
1 lb (upward)

(b) If a rope is tied to the block and run vertically over apulley, and the other end is attached to a free-hanging7.00 lb weight, what is the force exertedby the floor on the 15.0 lb block?
2 lb (upward)

(c) If we replace the 7.00 lb weight inpart (b) with a 23.0 lb weight, what isthe force exerted by the floor on the 15.0lb block?
3 lb (upward) (a) What force does the floor exert on theblock?
1 lb (upward)

(b) If a rope is tied to the block and run vertically over apulley, and the other end is attached to a free-hanging7.00 lb weight, what is the force exertedby the floor on the 15.0 lb block?
2 lb (upward)

(c) If we replace the 7.00 lb weight inpart (b) with a 23.0 lb weight, what isthe force exerted by the floor on the 15.0lb block?
3 lb (upward)

Explanation / Answer

a) The floor exerts 15 lb in the opposite direction of theweight, so the block remains motionless. b)Still applies the second law, by which the sum of forcesover a body determines its acceleration Floor_force +pulley_force - weight = 0 ( the block remainsmotionless) Ff = 8 lb c)Now the floor does not exert any force, because the forcecan only be upwards, and now the block is not at rest any more overthe floor. It tends to move upwards

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