Static Equilibrium Chapter 8 Questions Conditions for Equilibrium

Static Equilibrium • • Chapter 8 Questions ? ? ? Conditions for Equilibrium Example – Point objects Example – Table with no load Example – Table with off-center load. Example – Seesaws Example – Diving Boards Nat’s backyard Deck

Conditions for equilibrium •

Example 1 – Point Object •

Example 2 – Point Object •

Example 3 - Table • FA FB

Example 3 – with Torque • FA FB

Example 4 – Table with off-center load • FA FB

Example 5 –machine on table •

Example 6 - Seesaw • • • 2 children on seesaw – masses 25 kg, 30 kg Seesaw mass – 2 kg Child A distance - 2. 5 m. Find Child B distance x Free body diagram

Example 6 – Solving y and x •

Example 6 - Setting up torque •

Example 6 - Solving torque •

Example 7 – Diving Board •

Example 7 - Summary •

Example 7 – Torques around “A” •

Example 8 – Diving Board with weight •

Example 9 – Backyard Deck • Deck attached to 2 nd floor rear of house – 20 kg decking sections 4 m long – Support at 3 m, cantilever 1 m – 20 kg planter at 3. 5 m • Free body diagram (side view) planter Back of house

Example 9 – Solution • planter Back of house

Example 9 – 50 kg planter • planter Back of house

Torque Tips • Choose any point of rotation – Choose to minimize unknown variables – “Ridiculous” rotations OK • Evaluate individual torques – F┴. r (moment arms horz and vert) (strut/wire) – F. r┴ (forces horz and vert) (diagonal crane) – Diagonal moment arms mix x and y – All weights at CM • Add them all up – Keep aware of rotation point – CCW + , CW – by convention