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Consider the situation shown above. The coefficient of static friction is 0.60,
and the coefficient of kinetic friction is 0.45. |
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1. The two blocks are at rest. Assume the block mass is 0.250 kg, and the
hanging mass is 0.075 kg. What is the
static friction force acting on the block mass? |
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Not asked for
but a wise student would draw free body diagrams and write out the sum of the
force equations which produces: |
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If the masses
are not moving, a = 0. So the static
friction force fs is found from |
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We get T from
the Hanging mass equation |
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Substituting
that in |
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OVER à |
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2. What is the maximum possible static
friction force that could act on the block before it starts to move? |
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Maximum
possible static friction force is found from |
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From the sum of
the force equations |
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Plugging that
into max static friction equation |
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3. How much mass would the hanging mass have
to achieve this maximum static friction force? |
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Solving for
hanging mass |
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4. If the masses were moving, assuming the
mass of the block is still as 0.250 kg what is the magnitude of the kinetic
friction force acting on the block? |
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