Static Equilibrium Examples Evaluating individual torques Strut with
Static Equilibrium Examples • • Evaluating individual torques Strut with sign Ladder More complicated Ladder Traffic light with diagonal strut Pushing lamp across floor Door on hinges Pulling tire over curb
Torque Definition •
Torque Tips • Choose any point of rotation – 2 -D plane problems, x and y and one axis rotation – Choose to minimize unknown variables – “Ridiculous” rotations OK • Evaluate individual torques – – F┴. r (moment arms horz and vert) (strut/wire) “Type b” F. r┴ (forces horz and vert) (diagonal crane) “Type a” Diagonal moment arms mix x and y (wired gate) combination All finite object weights at CM • Add them all up – Keep aware of rotation point – CCW + , CW – by convention
Example 1 – Strut with sign • Free body diagram • Guess where forces must be – Weight down by beam – Weight down by sign – Force up at hinge – Force up by cable – Force to left by cable – Force to right at hinge
Example 1 – Strut with sign (2) •
Example 1 – Strut with sign (3) •
Example 2 - Ladder •
Example 2 – Ladder (2) •
Example 3 – More complicated ladder •
Example 3 – More complicated ladder (2) •
Example 4 -Traffic light on diagonal strut •
Example 4 -Traffic light on diagonal strut (2) •
Meter stick • • Ms weight at 50 cm CM Supports at 0 cm, 90 cm
Example 5 – Pushing lamp across floor •
Example 5 – Pushing lamp across floor (2) •
Example 6 - Door on hinges
Example 6 - Door on hinges (2) •
Example 6 - Door on hinges (3) •
Example 7 – Wheel on curb •
Example 7 – Wheel on curb (2) •
Example 7 – Wheel on curb (3) •
Other problems • Problem 23 – meter stick • Problem 22 – gymnast
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