Technician a says that the back of all engine bearings should be lubricated during assembly. technician b says that the face of the main and rod bearings should be lubricated before final assembly. which technician is correct?

Technician B is correct.

Explanation:

Friction is an oppositional force that tends to oppose the relative motion of two surfaces in contact. The two types are; static and dynamic friction. Because it generates heat and reduces the efficiency of a machine, it has to be reduced in machines.

Friction can be reduced either by; lubrication, polishing or smoothing, streamlining and the use of bearings. A bearing is a device that can be used to reduce friction between two moving parts. There is a need for the lubrication of the bearing during assembling to ensure its smooth running. Lubrication is a process of reducing friction between moving parts by the use of oil or grease.

The face of the main and rod bearings should be lubricated before final assembly because after the assembly, the rod is found to rotate within the main bearing. Thus, friction between these moving parts has to be reduced.

Engine bearings are used to reduce friction between the rotating part of the engine and the stationary part. Lubrication is important to avoid unnecessary noise, the disruption of the bearings and complete damage of the engine. Its internal part has to be lubricated and not the back, to increase the gripping at the back due to friction.

In both cases, lubrication is very important.      

at right angles to each other

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m