#  Forces in Equilibrium 

 



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## (Statics of Rigid Bodies)  
  


### Erector Spinae Muscle Forces

\[ L | t++ |★★★ \]   
A realistic model of the forces in the erector spinae muscles that support the back when bent over.

\[[In-Depth Description](/presentations/erector-spinae-muscle-forces)\]

### Tension Puzzler

\[M | t+ | ★★★\]   
Two weights tugging on a spring balance; to what result?  
  
\[[In-Depth Description](/presentations/tension-puzzler)\]

### Leaning Ladder

\[M | t | ★★\]  
Small ladder against wall with variable load and inclination.

\[[In-Depth Description](/presentations/leaning-ladder)\]

### Vector Sum of Forces

\[M | t | ★★\]  
Magnetic blackboard mechanics with spring balances and weights.

\[[In-Depth Description](/presentations/vector-sum-forces)\]

### Rectangle on Cylinder

\[M | t+ | ★★★\]  
What are the conditions for stable equilibrium?

\[[In-Depth Description](/presentations/rectangle-cylinder)\]

### Stack of Blocks

\[M | t | ★★★\]  
A dozen blocks are stacked on top of each other over the edge of the table seemingly defying gravity.

\[[In-Depth Description](/presentations/stack-blocks)\]

### Loaded Beam

\[M | t+ | ★★\]  
Beam supported at ends with platform scales and toy truck as load to demonstrate moment arms.

\[[In-Depth Description](/presentations/loaded-beam)\]

### Balancing Forks

\[s | t+ | ★★★\]   
Two forks, a cork, and a matchstick balance on the lip of a glass.

\[[In-Depth Description](/presentations/balancing-forks)\]

### Vector Arrows

\[M | t | ★\]  
Wooden arrow vectors, hand held or mountable.   
  
\[[In-Depth Description](/presentations/vector-arrows)\]

### Center of Mass

\[M | t+ | —\]   
Irregular lamina with marked center-of-mass tossed in air.

\[[In-Depth Description](/presentations/center-mass)\]

### Three-Legged Table

\[L | t | ★\]

Triangular table supported by platform scales.

\[[In-Depth Description](/presentations/three-legged-table)\]

### Friction Blocks

\[M | t | ★\]  
Selection of blocks that slide down a variable-angle inclined plane to demonstrate the various aspects of friction.

\[[In-Depth Description](/presentations/friction-blocks)\]

### Fakir Physics

\[M | t | ★★★\]  
The concept of pressure is demonstrated by lying on a bed of nails.

\[[In-Depth Description](/presentations/fakir-physics)\]

### Train on Circular Track

\[M | t | ★\]  
Vector representation of position, velocity, and acceleration.   
  
\[[In-Depth Description](/presentations/train-circular-track)\]

### Contact Us

**Mailing Address**: Lecture Demonstration Services, Science Center, Rm B-08A, 1 Oxford Street, Cambridge, MA 02138  
**Campus Location**: Science Center B-08A | **Tel**: (617) 495-5824 | **Email**: scidemos-at-fas.harvard.edu