Instructions

For the following questions answer them individually

Question 71

A force P is applied at a distance ā X ā from the end of the beam as shown in the figure. What would be value of ā X ā so that the displacement at āAā is equal to zero?

Question 72

An electric heater is sandwiched between two plates each 0.3 m long and 0.1 m wide with a thickness of 30 mm. At steady state condition the heater is maintained at a temperature of $$100^\circ C$$, with a current of 0.25 A and voltage of 200 V. Assume the plates are perfectly insulated at the edges, and the heater is having perfect contact with the plates to give a temperature of $$50^\circ C$$ on the outside of the plate surface. What is the thermal conductivity of the plate material?

Question 75

A torque T is applied at the free end of a stepped rod of circular cross-sections as shown in the figure. The shear modulus of the material of the rod is G. The expression for diameter ādā to produce an angular twist q at the free end is

Question 76

A pin jointed uniform rigid rod of weight 981 N and length 1 m is kept horizontally by an external force F as shown in the figure below. The force F is removed suddenly. At the instant of force removal, the magnitude of vertical reaction (in N) developed at the support is close to

Question 77

The frictional torque transmitted in a conical pivot bearing considering uniform pressure is : (R: radius of shaft,a : semi angle of cone, $$\mu$$ : Coefficient of friction, W: load on bearing)

Question 78

A mass of 2 kg is attached to two identical springs each with stiffness k = 40 kN/m as shown in the figure. Under friction less condition, the natural frequency of the system in Hz is close to

Question 79

A rectangular steel plate is joined to a vertical post using four identical rivets arranged as shown below in the figure. The shear load on the worst loaded rivet (in N) approximately is

Question 80

Match the following criterion of material failure under biaxial stresses $$\sigma_1$$ and $$\sigma_2$$ and yield stress $$\sigma_y$$ , with their corresponding graphic representations.