Engineering mechanics interview questions

              1. What are the various Types of friction?

                         Dry friction or Coulomb friction
                         Fluid friction
                         Lubricated friction
                         Skin friction
                         Internal friction

              2. Characteristics of dry friction?

 Friction is a force that resists the movement of two contacting surfaces that slide relative to one another.

This force always acts tangent to the surface at the points of contact and is directed so as to oppose the possible or existing motion between the surfaces.

             3. Friction is depends on Degree of roughness and area of contact?

                      No, friction force independent of these two.


              4. What is limiting friction?

                     The maximum resistance offered by the body is called limiting friction.

              5. What is coefficient of friction?

                      Ratio of limiting friction to the normal reaction.

                         Co-efficient of friction µ=Limiting friction /Normal reaction

              6. What is angle of friction?

                    Tangent of ratio of limiting friction to the Normal reaction.

                    tanɸ = limiting friction/Normal reaction

             7. What is meant by impending motion?

Just about to move or slide is called impending motion.

When the maximum frictional force is attained and if the applied force exceeds the limiting friction, the body start to slide or roll, that motion is called impending motion.

             8. Angle of repose?

The plane at which the body tends to slide down is known as angle of repose.

             9. State parallel axis theorem?

The moment of inertia of an area around any axis in its plane is equal to the moment of inertia of the same area around a parallel axis passing through the area’s centroid, plus the product of the same area and the square of the distance between the two axes.

I=I_G+Ah²

            10. State perpendicular axis theorem?

If I_xx is the area moment of inertia of a lamina about x-x axis in the plane of the lamina and I_yy is the area moment of inertia of a lamina about y-y axis (Perpendicular to the x-x axis) in the plane of the lamina, then I_zz, the polar area moment of inertia of the lamina about an axis perpendicular to the plane of the lamina (and perpendicular to the x-x axis and y-y axis) is given by

I_zz=I_xx +I_yy

            11. Write general equation for finding area moment of inertia?

I_xx=y²dA                        I_yy=X²dA

           12. Write general equation for finding area moment of inertia?

J=r²dA

Where

r-radius of the circle.