Aparticular conductor has 3.0 × 10^27 mobile electrons per cubic meter. the material is in the shape of a cylinder of length 6.0 cm and diameter 1.0 cm. when the bar is connected to a battery with an emf of 2.5 v, a current of 5.0 ma begins to flow.
what is the resistivity of the bar?

An engineer designs a roller coaster so that a car travels horizontally for 152 ft, then climbs 137 ft at an angle of 34.0° above the horizontal. it then moves 137 ft at an angle of 48.0° below the horizontal. if we take the initial horizontal motion of the car to be along the +x-axis, what is the car's displacement? (give the magnitude of your answer, in ft, to at least four significant figures and give the direction of your answer in degrees counterclockwise from the +x-axis.)

What tightening torque should be used for a hexagonal head screw (not split-bolt) on a 250 kcmil conductor?

Asolid round steel rod 6.25 mm in diameter and 375 mm long is rigidly bonded to the end of solid square brass rod 25 mm on a side and 300 mm long. the geometric axes of the bare are along the same line. an axial tensile force of 5.4 kn is applied at the extreme ends of the assembly. for steel e = 200 gpa and for brass e = 90 gpa. determine the total elongation for the assembly.