A copper wire has a diameter "d" is heated by a short circuit to "T_0" before a slow-blow fuse burns out. If the still air temperature is "T_a", how long will it take for the wire to drop to temperature "T", if the variable τ (tau) is found to be 0.02 hr ?
The following material properties are given:
k = 224 (BTU-ft/hr-ft2 -o R)
h = 1.65 (BTU/hr-ft2 -o R)
cp = 0.091 (BTU/lbm-o R)
rho = 558 (lbm/ft3 )
T_a = 99F
T = 139F
T_0 = 296F

Abrake has a normal braking torque of 2.8 kip in and heat-dissipating cast-iron surfaces whose mass is 40 lbm. suppose a load is brought to rest in 8.0 s from an initial angular speed of 1600 rev/min using the normal braking torque; estimate the temperature rise of the heat dissipating surfaces.

Amixture of slurry and mud is to be pumped through a horizontal pipe of diameter 500 mm. the fluid behaves as a bingham plastic with a yield stress of 30 pa and viscosity 0.04 pa.s. describe the effects of the shear stress through a transverse section of the pipe by plotting the variation in shear stress and velocity profile: (i) just before the slurry starts to move (ii) as the slurry flows when the pressure gradient is double that in part (i)

Asteel wire of 2 mm diameter is fixed between two points located 2 m apart. the tensile force in the wire is 250n, if its density of steel is given by 7830 kg/m3 the fundamental frequency of vibration hz? ?