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AP® Physics C: Mechanics

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Moderate

Three Masses on a Balance Beam

APPHMC-BKTES2

Nick Borowicz. Created for Albert.io. Copyright 2016. All rights reserved.

A $2\text{ kg}$ mass is placed with its center of mass at $x= -10 \text{ cm}$ to the left of the fulcrum on a balance beam, as shown above. Two identical masses $m$ are placed with their centers of mass at $x=40\text{ cm}$ and $x=70\text{ cm}$ to the right of the fulcrum. The mass of the balance beam is negligible.

What must be the value of $m$ in order for the system to be in rotational equilibrium?

A

$0.02\text{ kg}$

B

$0.2 \text{ kg}$

C

$0.5\text{ kg}$

D

$1\text{ kg}$

E

$2\text{ kg}$