UNIVERSITY of PLYMOUTH

 

MECH115: Engineering Science 1

 

Tutorial examples: - Forces in Pin-Jointed Structures           [Use g = 9.81 m/s² where required]

 

  1. The simple pinjointed frame shown below is designed to support a mass of 10 tonnes maximum suspended from A. Find the forces in the members AB and AC. State which is a tie and which a strut. BC is vertical.         [ FAB=148.1 kN, FAC=137.2 kN]

 

 

 

 

 

 

 

 

 

 

 

 


  1. The bellcrank shown below supports forces as shown. Determine the force in the push rod at B required to just rotate the bellcrank about is fulcrum A, and also find the force reaction at A. AB=12cm, AD =14cm, AC =7cm.                                 [370.3 N, 450 N]

 

 

 

 

 

 

 

 

 

 

 

 

 


  1. A motor car jack supports a load of 0.5 tonne as shown below. Find the tension force in the horizontal threaded shaft.                                              [ 5.886 kN (equiv. of 0.6 tonnes)]

 

 

                                   

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. A push rod in a motor car gear linkage mechanism is attached to the lower end of the gear lever as shown below. If it is made from steel of 5mm diameter. If the driver pushes or pulls the gear lever knob with a force of  260N find the stress developed in the push rod.        [66.2 MN/m²]

 

 

                                                           

 

 

 

 

 

 

 

 

 

 

 

  1. A steel wire of 2mm diameter and 12 m in length is subject to a force of 1 kN.
    What is the tensile stress in the wire and how much does it stretch.
    Assume Esteel = 200GN/m2.  [ 318.3 MN/m2, 19.1 mm]

 

  1. A rubber engine mount shown below has a cross section 4 cm by 10 cm. It is 3 cm in thickness. Find shear stress in the rubber and the angle it assumes when subject to an engine mounting shear load of 500 N. The shear modulus for rubber is 0.9 kN/m2.  [125 kN/m2, 8º ]

 

 

 

 

 

 

 

 


  1. In older cars brake linings were held onto brake shoes using brass rivets. If the tangential force applied to the brake lining (tending to slide it over the shoe) was 3000N, find the shear stress in the rivets if there were 8 rivets in total each of 3.18 mm in diameter.
    Assume the shear load is divided equally and there is no friction between the brake lining and the brake shoe.    [47.2 MN/m² ]

 

  1. A shearing die blanks out circular discs of diameter 134 mm from 18 gauge (1.219mm) brass plate. In order to cut the brass an ultimate shear stress (USS) of 220 MN/m² is required. Determine the force which must be applied to the die.  [112.9 kN]

 

 

 

 

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