Prelim Srb

MOMENTS

1.)

The 4-kN force F is applied at point A. Compute the moment of F about point O, expressing it both as a scalar and as a vector quantity. Determine the coordinates of  the points on the x- and y-axes about which the moment of F is zero.

[ √    √  ]                        Coordinates of intercepts intercepts : ( -1.3 , 0 ) , ( 0 , 0.78 )

2.)

The rectangular plate is made up of 1-ft squares as shown. A 75-lb force is applied at point A in the direction shown. Determine the moment of this force about point B and about point C.

      [√  ]        [√    √  ]         

3.)

A prybar is used to remove a nail as shown. Determine the moment of the 60-lb force about the point O of contact between the prybar and the small support block.

              

4.)

The entire branch OA has a mass of 180 kg with mass center at G. Determine the moment of the weight of this branch about point O.

     

5.)

The 30-N force P is applied perpendicular to the portion BC of the bent bar. Determine the moment of P about point B and about point A.

               

Resultants

1.) Determine the resultant R of the three tension forces acting on the eye bolt. Find the magnitude of R and the angle θx which R makes with the positive x-axis.

                        ( )      

2.) Determine and locate the resultant R of the two forces and one couple acting on the Ibeam.

         ||           

3.) If the resultant of the two forces and couple M passes through point O, determine M.

            

4.) A commercial airliner with four jet engines, each producing 90 kN of forward thrust, is in a steady, level cruise when engine number 3 suddenly fails. Determine and locate the resultant of the three remaining engine thrust vectors. Treat this as a two -dimensional problem.

                    

5.) While sliding a desk toward the doorway, three students exert the forces shown in the overhead view. Determine the equivalent force-couple system at point A. Then determine the equation of the line of action of the resultant force.

                                         

Equilibriums 1.) The mass center G of the 1400-kg rear-engine car is located as show in the figure. Determine the normal force under each tire when the car is in equilibrium. State any assumptions.

                           

2.) A carpenter carries a 12-lb 2-in. by 4-in. board as shown. What downward force does he feel on his shoulder at A?

        

3.) A carpenter holds a 12-lb 2in. by 4-in. board as shown. If he exerts vertical forces on the board, determine the forces at A and B.

                      

4.) The 450-kg uniform I-beam supports the load shown. Determine the reactions at the supports.

                                

5.) The 20-kg homogeneous smooth sphere rests on the two inclines as shown. Determine the contact forces at A and B.

                   