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Forces and Moments Effects

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a. what is the force acting through (F) required to hold the lever in static equilibrium? Indicate clearly the Force and resistance vectors due to the weight, the force moment arm and the resistance moment arm, as well as the axis. Note that the weight is 40 kg and gravity is g=9.81 m/s2.

b. What would be the effect if the force increased 2 folds? Is static equilibrium maintained while the moment arms remain constant, as presented in (a)? Draw a figure and explain.

c. What is the net (combined) moment created in figure (a) if the resistance is now 122 Kg, and the force acting through F is 200 N? Is it clockwise or counterclockwise? Moment arms are constant for the force and the resistance.

d. what class of lever is represented in (a) as indicated by the three main components: Force, resistance and axis? in your opinion, what is the mechanical advantage of this system? Is it in favor of speed or strength?

Tip from the professor:
Mechanical advantage(MA)= load/torque, or Resistance/force, or force arm/resistancearm
You have the force arm and the resistance arm. That should give you the MA and a smallresearch should indicate if the value obtained favors speed or strength (force)

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The forces and moments effects are examined.

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Force and moment

1. Jane, a 120 lb woman, trips while walking down the street. She stumbles forward and falls onto her outstretched right hand. At the instant Jane's hand contacts the ground her whole body is moving downward at a velocity of 9 m/s and has a downward acceleration of 9.8 m/s2 (gravity). Her body rapidly decelerates after contacting the ground; after 0.04 seconds it has stopped moving.

Assuming that Jane's entire body mass is halted in 0.04 seconds, how much force did Jane's hand experience? (Hint: F=ma)

2. When Jane hit the ground with her hands, her wrist was extended at 45° and her elbow was bent at 45°. The length of her forearm is 27 cm and her upper arm is 32 cm.

Assuming the ground reaction force is acting directly vertically, what is the moment about Jane's elbow?

3. What assumptions can one make when answering questions 1 and 2?

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