# STATICS

1J10.10 CENTER OF MASS OF STATE
1J11.20 LEANING TOWER STABILITY
1J20.55 STABILITY OF VERTICAL ROD
1J30.10 SUSPENDED BLOCK FORCES
1J30.25 TENSION IN ROPE
1J40.20 METER STICK BALANCE
1J40.40 SUSPENDED STATIC BEAM

 1J10.10 Map of the State Suspend a map of the state from various holes to determine "center of mass". Use chalk or erasable marker to draw lines on map. Setup Requirements: minimal   Equations: center of mass = sum( mi x ri ) / sum mi   Safety Issues: none

 1J11.20 Leaning tower of Lire Blocks are stacked so top block extends beyond bottom block. Setup Requirements: Off the Shelf   Equations: Stable if center of mass and line connecting with center of Earth falls inside base.   Safety Issues: None

 1J20.55 Stability of Vertical Rod Usually when stability is talked about a lower position of the center of mass is considered more stable like in the rollover problems with some vehicles. This demonstration shows there is another factor to consider with a tall thin object. Is it easier to rotate if the mass is close to your hand or near other end of the rod? Try it and see.   Setip Requirements: Minimal. Adjust position of mass. Equations:  T = I a.  I~ M x square of distance. Safety Issue: Htting things with rod. Mass coming loose.

 1J30.10 Suspended Block Adjust masses on weight holder until forces balanced. Remove inclined plane. Normal force, weight and tension will balance so object does not move. Can adjust to different angles. Setup Requirements: Ask ahead of time. Some time needed to assemble and adjust.   Equations: N= W cos(A), T=Wsin(A)   Safety Issues: none

 1J30.25 Rope and Three Students Two large students pull rope at both ends and a smaller student pushes down in the middle. As rope is straightened angle decreases and T needed to keep straight increases toward infinity. Setup Requirements: Minimal   Equations: T sin(A) = mg/2 or F(student)/2.   Safety Issues: None

 1J40.20 Meter Stick Balance Hang various weights from different positions on balance beam. Adjust so torques balanced. Demonstrate how balance works. Demonstrate torque depends on F and r. Setup Requirements: Minimal. Version provided may differ from picture.   Equations: Torque = rFsin(A)   Safety Issues: None

 IJ40.40 Suspended Static Beam Place weights at different positions on rod to see effect on scale reading.      Setup Requirements: Ask ahead of time. Assembled as needed. Requires the special table with holes for rods. Equations: Sum of forces = 0 and Sum of Torques = 0 when balanced. Torque = r x F Safety Issues: Dropping heavy weights.