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STATICS - CASE STUDY

    Introduction


Problem Description Animation
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A utility truck uses an extendible arm to raise and lower supplies and equipment. If the arm is raised and then rotated perpendicular to the length of the truck, it will affect the equilibrium of the truck.

What is known:

  • The initial length of the arm is 8 m.
  • The arm is raised 30° above the horizontal.
  • The mass of the truck is 2,000 kg.
  • The arm is hoisting a 400 kg load of bricks.
  • The mass of the arm and the length of the truck can be neglected.
     
    Question


Dimension Diagram

 

When the arm reaches a stable position perpendicular to the length of the truck and 30° up from the horizontal, what are the normal forces exerted on the right and left wheels by the ground?

   
  Approach

 
  • Assume that the normal forces acting on the wheels, the center of mass of the truck, and the center of mass of the bricks all lie in the same plane.
  • Make a free-body diagram.
  • Sum the forces and moments acting on the truck.
  • Solve for the normal forces acting on the wheels.