Kevin S. Huang

2007: Problem 12

Topic: Dynamics
Concepts: Statics, Torque from weight

Solution:

Balancing torques around the fulcrum, we have

mgl_1=Mgl_2

using the fact that we can put all the weight of the measuring stick at its center of mass to find the equivalent torque. Since $l_1=0.2\,\mathrm{m}$ , we have $l_2=0.5\,\mathrm{m}-l_1=0.3\,\mathrm{m}$ . Thus,

M=\frac{l_1}{l_2}m=\frac{0.2\,\mathrm{m}}{0.3\,\mathrm{m}}(2\,\mathrm{kg})=1.33\,\mathrm{kg}

so the answer is C.

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Kevin S. Huang

2007: Problem 12

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2007: Problem 12

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