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The screw jack of Fig. screw having a coefficient of friction of 0.35 and a mean ra- dius of 1 in. Determine the maximum lead such that uses a square-threaded. The moment necessary to lower the jack is 20 percent of the moment necessary to raise the jack.

The screw jack of Fig. screw having a coefficient of friction of 0.35 and a mean ra- dius of 1 in. Determine the maximum lead such that uses a square-threaded. The moment necessary to lower the jack is 20 percent of the moment necessary to raise the jack.

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The screw jack of Fig. screw having a coefficient of friction of 0.35 and a mean ra- dius of 1 in. Determine the maximum lead such that uses a square-threaded. The moment necessary to lower the jack is 20 percent of the moment necessary to raise the jack.
Transcribed Image Text:The screw jack of Fig. screw having a coefficient of friction of 0.35 and a mean ra- dius of 1 in. Determine the maximum lead such that uses a square-threaded. The moment necessary to lower the jack is 20 percent of the moment necessary to raise the jack.
Expert Solution
Step 1

Given data:

  • The coefficient of friction is μs=0.35.
  • The mean radius is r=1 in.

Free body diagram of a partial section of screw thread as it advances:

Advanced Physics homework question answer, step 1, image 1

Force triangle of a partial section of the screw as it advances is shown:

Advanced Physics homework question answer, step 1, image 2

Free body diagram of a partial section of screw thread as it unwinds:

Advanced Physics homework question answer, step 1, image 3

Force triangle of a partial section of the screw as it unwinds is shown:

Advanced Physics homework question answer, step 1, image 4

The moment necessary to lower the jack is 20% of the moment necessary to raise the jack,

Ml=20%×MuMl=0.20Mu

The angle of friction is given by,

ϕs=tan-1μsϕs=tan-10.35ϕs=19.29∘

From the force triangle as the screw advances,

tanϕs+α=MurWtan19.29°+α=MurWMur=W×tan19.29°+α.........................(1)

 

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