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AP® Physics 1 & 2

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Equilibrium with Friction

APPH12-NGAFGE

Consider the two block system in the image. One block ($mass = 4m$) is sitting on a table connected by a rope over a pulley to another block ($mass = 3m$) hanging in the air. There is a frictional force between the block resting on the table and the table.

What frictional force, $f$, is needed for the system to remain in equilibrium once released?

A

$f = 3mg$

B

$f = mg$

C

$f = 3mg - 7ma$

D

$f = 4ma$