Summary

• Static equilibrium

• Stability & balance
  • stable equilibrium
  • unstable equilibrium
  • neutral equilibrium
    Example #1
    
    Example #2
    
  
  
  
• Elastic properties of solids
  • stress & strain
  • elastic modulii
    • Young's modulus
      applet
    • shear modulus
      applet
    • bulk modulus
      applet
      Example #3
      
      Example #4
      
  
  

sj6 12.24
Two identical, uniform bricks of length L are stacked as shown. What is the maximum x without falling?
A. L      B. 3L/4      C. L/2      D. L/3

Answer







gc6 9.36
The Leaning Tower of Pisa is 55 m tall and about 7.0 m in diameter. The top is 4.5 m off center. How much farther can it lean before it becomes unstable?
A. 1.0 m
B. 2.5 m
C. 3.5 m
D. 4.5 m
Answer







sj6 12.34
A 2.0 m long, 4.0 mm diameter steel wire is placed over a pulley with 5.0 kg and 3.0 kg masses hung on its ends. By how much does it stretch while in motion?
A. 1.76 mm          B. 0.312 mm
C. 29.2 µm           D. 4.33 µm
Answer







sj6 12.36
What is the density of sea water at a depth of 11 km if the pressure there is 113 MPa and the surface ρ=1030 kg/m³?
A. 1035 kg/m³           B. 1049 kg/m³
C. 1089 kg/m³           D. 1476 kg/m³
Answer







 



B. 3L/4
The center of mass of the first brick must be above the point of support, and the center of mass of the two-brick combination must also be above its point of support.












 



B. 2.5 m
The top would have to move one diameter in order to put the center gravity, assumed to be halfway down, over the pivot point of one side of the base. It can therefore move 7.0 m - 4.5 m = 2.5 m further.












 



C. 29.2 µm













 



C. 1089 kg/m³